Filter Effects 1.0

Abstract

Filter effects are a way of processing an element's rendering before it is displayed in the document. Typically, rendering an element via CSS or SVG can conceptually be described as if the element, including its children, are drawn into a buffer (such as a raster image) and then that buffer is composited into the elements parent. Filters apply an effect before the compositing stage. Examples of such effects are blurring, changing color intensity and warping the image.

Although originally designed for use in SVG, filter effects are a set of operations to apply on an image buffer and therefore can be applied to nearly any presentational environment, including CSS. They are triggered by a style instruction (the ‘filter’ property). This specification describes filters in a manner that allows them to be used in content styled by CSS, such as HTML and SVG. It also defines a CSS property value function that produces a CSS <image> value.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

The (archived) public mailing list public-fx@w3.org (see instructions) is preferred for discussion of this specification. When sending e-mail, please put the text “filter-effects” in the subject, preferably like this: “[filter-effects] …summary of comment…”

This document was produced by the CSS Working Group (part of the Style Activity) and the SVG Working Group (part of the Graphics Activity).

This document was produced by groups operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures (CSS) and a public list of any patent disclosures (SVG) made in connection with the deliverables of each group; these pages also include instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

The list of changes made to this specification is available.

Table of contents

• 1. Introduction
• 2. Module interactions
• 3. Values
• 4. Definitions
• 5. The ‘filter’ property
• 6. The <filter> element
• 7. Filter effects region
• 8. Filter primitives
  • 8.1. Overview
  • 8.2. Common attributes
  • 8.3. Filter primitive subregion
  • 8.4. Filter primitive <feBlend>
  • 8.5. Filter primitive <feColorMatrix>
  • 8.6. Filter primitive <feComponentTransfer>
  • 8.7. Filter primitive <feComposite>
  • 8.8. Filter primitive <feConvolveMatrix>
  • 8.9. Filter primitive <feCustom>
  • 8.10. Filter primitive <feDiffuseLighting>
  • 8.11. Filter primitive <feDisplacementMap>
  • 8.12. Filter primitive <feDropShadow>
  • 8.13. Filter primitive <feFlood>
    • 8.13.1. The ‘flood-color’ property
    • 8.13.2. The ‘flood-opacity’ property
  • 8.14. Filter primitive <feGaussianBlur>
  • 8.15. Filter primitive <feImage>
  • 8.16. Filter primitive <feMerge>
  • 8.17. Filter primitive <feMorphology>
  • 8.18. Filter primitive <feOffset>
  • 8.19. Filter primitive <feSpecularLighting>
  • 8.20. Filter primitive <feTile>
  • 8.21. Filter primitive <feTurbulence>
• 9. The ‘color-interpolation-filters’ property
• 10. Light source elements and properties
  • 10.1. Introduction
  • 10.2. Light source <feDistantLight>
  • 10.3. Light source <fePointLight>
  • 10.4. Light source <feSpotLight>
  • 10.5. The ‘lighting-color’ property
• 11. Custom Filter Function
  • 11.1. The ‘@supports’ condition: ‘filter’
  • 11.2. The @filter rule
  • 11.3. Custom filter resources: the src descriptor
  • 11.4. Custom filter parameters: the parameters descriptor
  • 11.5. Custom filter geometry: the geometry descriptor
  • 11.6. Custom filter compositing: the mix descriptor
  • 11.7. Custom filter margins: the margin descriptor
• 12. Custom Shaders
  • 12.1. Introduction
  • 12.2. Precedents
  • 12.3. Recommended shading language
  • 12.4. Integration into Custom Filter Functions
  • 12.5. Shader Processing Model
  • 12.6. Differences to GLSL
    • 12.6.1. Fragment Shaders Differences with GLSL
    • 12.6.2. Vertex attribute variables
    • 12.6.3. Shader uniform variables
    • 12.6.4. Other uniform variables: the CSS shaders parameters
    • 12.6.5. Default shaders
    • 12.6.6. Texture access
• 13. The filter CSS <image> value
• 14. Shorthands defined in terms of the <filter> element
  • 14.1. grayscale
  • 14.2. sepia
  • 14.3. saturate
  • 14.4. hue-rotate
  • 14.5. invert
  • 14.6. opacity
  • 14.7. brightness
  • 14.8. contrast
  • 14.9. blur
  • 14.10. drop-shadow
  • 14.11. custom
• 15. The ‘enable-background’ property
  • 15.1. Accessing the background image in SVG
• 16. Integration with CSS Animations and CSS Transitions
  • 16.1. Interpolating filter function parameters
  • 16.2. Interpolating the shader-params component in the custom() function.
• 17. Security
  • 17.1. Rendered Content Access in custom filter primitives
  • 17.2. Origin Restrictions
• 18. DOM interfaces
  • 18.1. Interface SVGFilterElement
  • 18.2. Interface SVGFilterPrimitiveStandardAttributes
  • 18.3. Interface SVGFEBlendElement
  • 18.4. Interface SVGFEColorMatrixElement
  • 18.5. Interface SVGFEComponentTransferElement
  • 18.6. Interface SVGComponentTransferFunctionElement
  • 18.7. Interface SVGFEFuncRElement
  • 18.8. Interface SVGFEFuncGElement
  • 18.9. Interface SVGFEFuncBElement
  • 18.10. Interface SVGFEFuncAElement
  • 18.11. Interface SVGFECompositeElement
  • 18.12. Interface SVGFEConvolveMatrixElement
  • 18.13. Interface SVGFECustomElement
  • 18.14. Interface SVGFECustomSourceElement
  • 18.15. Interface SVGFECustomParamElement
  • 18.16. Interface SVGFEDiffuseLightingElement
  • 18.17. Interface SVGFEDistantLightElement
  • 18.18. Interface SVGFEPointLightElement
  • 18.19. Interface SVGFESpotLightElement
  • 18.20. Interface SVGFEDisplacementMapElement
  • 18.21. Interface SVGFEDropShadowElement
  • 18.22. Interface SVGFEFloodElement
  • 18.23. Interface SVGFEGaussianBlurElement
  • 18.24. Interface SVGFEImageElement
  • 18.25. Interface SVGFEMergeElement
  • 18.26. Interface SVGFEMergeNodeElement
  • 18.27. Interface SVGFEMorphologyElement
  • 18.28. Interface SVGFEOffsetElement
  • 18.29. Interface SVGFESpecularLightingElement
  • 18.30. Interface SVGFETileElement
  • 18.31. Interface SVGFETurbulenceElement
• 19. Conformance
• 20. References
  • Normative references
  • Other references
• Changes
• Property index
• Index

1. Introduction

A filter effect is a graphical operation that is applied to an element as it is drawn into the document. It is an image-based effect, in that it takes zero or more images as input, a number of parameters specific to the effect, and then produces an image as output. The output image is either rendered into the document instead of the original element, used as an input image to another filter effect, or provided as a CSS image value.

A simple example of a filter effect is a "flood". It takes no image inputs but has a parameter defining a color. The effect produces an output image that is completely filled with the given color. A slightly more complex example is an "inversion" which takes a single image input (typically an image of the element as it would normally be rendered into its parent) and adjusts each pixel such that they have the opposite color values.

Filter effects are exposed with three levels of complexity:

1. A small set of canned filter functions that are given by name. While not particularly powerful, these are convenient and easily understood and provide a simple approach to achieving common effects, such as blurring.
2. A graph of individual filter effects described in markup that define an overall effect. The graph is agnostic to its input in that the effect can be applied to any content. While such graphs are the combination of effects that may be simple in isolation, the graph as a whole can produce complex effects. An example is given below.
3. A customizable system that exposes a shading language allowing control over the geometry and pixel values of filtered output.

The following shows an example of a filter effect.

Initial example for a filtered object.

View this example as SVG

The filter effect used in the example above is repeated here with reference numbers in the left column before each of the six filter primitives:

 
 
1
2
3
 
 
 
 
4
5
 
6
 
 
 

<filter id="MyFilter" filterUnits="userSpaceOnUse" x="0" y="0" width="200" height="120">
  <desc>Produces a 3D lighting effect.</desc>
  <feGaussianBlur in="SourceAlpha" stdDeviation="4" result="blur"/>
  <feOffset in="blur" dx="4" dy="4" result="offsetBlur"/>
  <feSpecularLighting in="blur" surfaceScale="5" specularConstant=".75" 
                      specularExponent="20" lighting-color="#bbbbbb" 
                      result="specOut">
    <fePointLight x="-5000" y="-10000" z="20000"/>
  </feSpecularLighting>
  <feComposite in="specOut" in2="SourceAlpha" operator="in" result="specOut"/>
  <feComposite in="SourceGraphic" in2="specOut" operator="arithmetic" 
               k1="0" k2="1" k3="1" k4="0" result="litPaint"/>
  <feMerge>
    <feMergeNode in="offsetBlur"/>
    <feMergeNode in="litPaint"/>
  </feMerge>
</filter>

The following pictures show the intermediate image results from each of the six filter elements:

1. Filter primitive <feGaussianBlur> takes input SourceAlpha, which is the alpha channel of the source graphic. The result is stored in a temporary buffer named "blur". Note that "blur" is used as input to both filter primitives 2 and 3.
2. Filter primitive <feOffset> takes buffer "blur", shifts the result in a positive direction in both x and y, and creates a new buffer named "offsetBlur". The effect is that of a drop shadow.
3. Filter primitive <feSpecularLighting>, uses buffer "blur" as a model of a surface elevation and generates a lighting effect from a single point source. The result is stored in buffer "specOut".
4. Filter primitive <feComposite> masks out the result of filter primitive 3 by the original source graphics alpha channel so that the intermediate result is no bigger than the original source graphic.
5. Filter primitive <feComposite> composites the result of the specular lighting with the original source graphic.
6. Filter primitive <feMerge> composites two layers together. The lower layer consists of the drop shadow result from filter primitive 2. The upper layer consists of the specular lighting result from filter primitive 5.

2. Module interactions

This specification defines a set of CSS properties that affect the visual rendering of elements to which those properties are applied; these effects are applied after elements have been sized and positioned according to the Visual formatting model from [CSS21]. Some values of these properties result in the creation of a containing block, and/or the creation of a stacking context.

Some property and element definitions in this specification require an SVG 1.1 implementation [SVG11]. UAs without support for SVG must not implement the ‘color-interpolation-filters’, ‘flood-color’, ‘flood-opacity’ and ‘lightning-color’ properties as well as the <filter> element, the <feMergeNode> element, the <feCustomParam> element, the transfer function elements and the filter primitive elements.

3. Values

This specification follows the CSS property definition conventions from [CSS21]. Value types not defined in this specification are defined in CSS Level 2 Revision 1 [CSS21].

In addition to the property-specific values listed in their definitions, all properties defined in this specification also accept the inherit keyword as their property value. For readability it has not been repeated explicitly.

4. Definitions

When used in this specification, terms have the meanings assigned in this section.

null filter

The null filter output is all transparent black pixels. If applied to an element it means that the element (and children if any) becomes invisible. Note that it does not affect event processing.

transfer function elements

The set of <feFuncR>, <feFuncG>, <feFuncB>, <feFuncA> elements, that define the transfer function for the <feComponentTransfer> filter primitive.

bounding client rect

The union of all border boxes for the element that has an associated CSS layout box and is not in the https://www.w3.org/2000/svg namespace and it's descendant elements. Or the object bounding box [SVG11], if the element does not have an associated CSS layout box and is in the https://www.w3.org/2000/svg namespace (See getBoundingClientRect [CSSOM]]).

local coordinate system

In general, a coordinate system defines locations and distances on the current canvas. The current local coordinate system (also user coordinate system) is the coordinate system that is currently active and which is used to define how coordinates and lengths are located and computed, respectively, on the current canvas [CSS3-TRANSFORMS].

For elements that have an associated CSS layout box, the current user coordinate system has its origin at the top-left corner of the bounding client rect and one unit equals one CSS pixel. The viewport for resolving percentage values is defined by the width and height of the bounding client rect.

If the element does not have an associated CSS layout box and is in the https://www.w3.org/2000/svg namespace, the current local coordinate system has its origin at the top-left corner of the element's nearest viewport.

user coordinate system

See definition of local coordinate system.

object bounding box units

The bounding client rect defines the coordinate system in which to resolve values, as defined in object bounding box units [SVG11].

filter primitives, filter primitive elements

The set of elements that control the output of a <filter> element, particularly: <feSpotLight>, <feBlend>, <feColorMatrix>, <feComponentTransfer>, <feComposite>, <feConvolveMatrix>, <feCustom>. <feDiffuseLighting>, <feDisplacementMap>, <feDropShadow>, <feFlood>, <feGaussianBlur>, <feImage>, <feMerge>, <feMorphology>, <feOffset>, <feSpecularLighting>, <feTile>, <feTurbulence>,

light sources

The following elements are light sources: <feDistantLight>, <fePointLight>, <feSpotLight>.

filter primitive attributes

All filter primitives share ‘x’, ‘y’, ‘width’ and ‘height’ as filter primitive attributes.

vertex mesh

The vertex mesh defines the geometry that is processed by the vertex shader.

5. The ‘filter’ property

The description of the ‘filter’ property is as follows:

If the value of the ‘filter’ property is ‘none’ then there is no filter effect applied. Otherwise, the list of functions are applied in the order provided.

<filter-function> = <URL> | grayscale(<number> | <percentage>)
 | sepia(<number> | <percentage>) | saturate(<number> | <percentage>)
 | hue-rotate(<angle>) | invert(<number> | <percentage>)
 | opacity(<number> | <percentage>) | brightness(<number> | <percentage>)
 | contrast(<number> | <percentage>) | blur(<length>) | drop-shadow([<length>{2,3} && <color>?]#)
 | custom(IDENT [, <param>]*)

<URL>

A URL reference to a <filter> element. For example ‘url(commonmasks.xml#mask)’. If the URL references a non-existent object or the referenced object is not a <filter> element, then the null filter will be applied instead.

grayscale(<number> | <percentage>)

Converts the input image to grayscale. The passed parameter defines the proportion of the conversion. A value of 100% is completely grayscale. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

sepia(<number> | <percentage>)

Converts the input image to sepia. The passed parameter defines the proportion of the conversion. A value of 100% is completely sepia. A value of 0 leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

saturate(<number> | <percentage>)

Saturates the input image. The passed parameter defines the proportion of the conversion. A value of 0% is completely un-saturated. A value of 100% leaves the input unchanged. Other values are linear multipliers on the effect. Values of amount over 100% are allowed, providing super-saturated results. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

hue-rotate(<angle>)

Applies a hue rotation on the input image. The passed parameter defines the number of degrees around the color circle the input samples will be adjusted. A value of 0deg leaves the input unchanged. If the parameter is missing, a value of 0deg is used. Implementations should not normalize this value in order to allow animations beyond 360deg. The markup equivalent of this function is given below.

invert(<number> | <percentage>)

Inverts the samples in the input image. The passed parameter defines the proportion of the conversion. A value of 100% is completely inverted. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

opacity(<number> | <percentage>)

Applies transparency to the samples in the input image. The passed parameter defines the proportion of the conversion. A value of 0% is completely transparent. A value of 100% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. This is equivalent to multiplying the input image samples by amount. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

The opacity filter function is not meant to be a shorthand of the ‘opacity’ property. Furthermore, it allows setting the transparency of intermediate filter primitive results before passing to the next filter primitive. If the opacity filter function is set as last filter primitive, the value of the ‘opacity’ property is multiplied on top of the value of the filter function, which may result in a more transparent content.

brightness(<number> | <percentage>)

Applies a linear multiplier to input image, making it appear more or less bright. A value of ‘0%’ will create an image that is completely black. A value of ‘100%’ leaves the input unchanged. Other values are linear multipliers on the effect. Values of amount over 100% are allowed, providing brighter results. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

contrast(<number> | <percentage>)

Adjusts the contrast of the input. A value of ‘0%’ will create an image that is completely gray. A value of ‘100%’ leaves the input unchanged. Values of amount over 100% are allowed, providing results with less contrast. If the parameter is missing, a value of 100% is used. The markup equivalent of this function is given below.

blur(<length>)

Applies a Gaussian blur to the input image. The passed parameter (the radius) defines the value of the standard deviation to the Gaussian function. If no parameter is provided, then a value 0 is used. The parameter is specified a CSS length, but does not accept percentage values. The markup equivalent of this function is given below.

The FXTF is looking into distinguish between vertical and horizontal blur radii.

drop-shadow([<length>{2,3} && <color>?]#)

Applies a drop shadow effect to the input image. A drop shadow is effectively a blurred, offset version of the input image's alpha mask drawn in a particular color, composited below the image. Values are interpreted as for ‘box-shadow’ [CSS3BG]. (But note that spread values are not allowed.) The markup equivalent of this function is given below.

custom(IDENT [, <param>]*)

References a custom filter at-rule by the given identifier. See Custom Filter Function for details.

The first function in the list takes the element (SourceGraphic) as the input image. Subsequent operations take the output from the previous function as the input image. The exception is the function that references a <filter> element, which can specify an alternate input, but still uses the previous output as its SourceGraphic.

The application of the ‘filter’ property to an element formatted with the CSS box model establishes a new stacking context the same way that CSS ‘opacity’ does, and all the element's descendants are rendered together as a group with the filter effect applied to the group as a whole.

The ‘filter’ property has no effect on the geometry of the target element's CSS boxes, even though ‘filter’ can cause painting outside of an element's border box.

Conceptually, any parts of the drawing are effected by filter operations. This includes any content, background, borders, text decoration, outline and visible scrolling mechanism of the element to which the filter is applied, and those of its descendants. The filter operations are applied in the element's local coordinate system.

The compositing model follows the SVG compositing model [SVG11]: first any filter effect is applied, then any clipping, masking and opacity. As per SVG, the application of ‘filter’ has no effect on hit-testing.

The CSS WG wants to look into how to apply the filter to certain parts of an object (background, border) instead of just the whole group with descendants.

6. The <filter> element

The description of the <filter> element follows:

Properties inherit into the <filter> element from its ancestors; properties do not inherit from the element referencing the <filter> element.

<filter> elements are never rendered directly; their only usage is as something that can be referenced using the ‘filter’ property. The ‘display’ property does not apply to the <filter> element; thus, <filter> elements are not directly rendered even if the ‘display’ property is set to a value other than none, and <filter> elements are available for referencing even when the ‘display’ property on the <filter> element or any of its ancestors is set to none.

7. Filter effects region

A <filter> element can define a region on the canvas to which a given filter effect applies and can provide a resolution for any intermediate continuous tone images used to process any raster-based filter primitives. The <filter> element has the following attributes which work together to define the filter effects region:

‘filterUnits’

Defines the coordinate system for attributes ‘x’, ‘y’, ‘width’, ‘height’.

If ‘filterUnits’ is equal to ‘userSpaceOnUse’, ‘x’, ‘y’, ‘width’, ‘height’ represent values in the current user coordinate system in place at the time when the <filter> element is referenced (i.e., the user coordinate system for the element referencing the <filter> element via a ‘filter’ property).

If ‘filterUnits’ is equal to ‘objectBoundingBox’, then ‘x’, ‘y’, ‘width’, ‘height’ represent fractions or percentages of the bounding box on the referencing element (see object bounding box units).

The lacuna value for ‘filterUnits’ is ‘objectBoundingBox’.

Animatable: yes.

‘x’, ‘y’, ‘width’, ‘height’

These attributes define a rectangular region on the canvas to which this filter applies.

The amount of memory and processing time required to apply the filter are related to the size of this rectangle and the ‘filterRes’ attribute of the filter.

The coordinate system for these attributes depends on the value for attribute ‘filterUnits’.

The bounds of this rectangle act as a hard clipping region for each filter primitive included with a given <filter> element; thus, if the effect of a given filter primitive would extend beyond the bounds of the rectangle (this sometimes happens when using a <feGaussianBlur> filter primitive with a very large ‘stdDeviation’), parts of the effect will get clipped.

The lacuna value for ‘x’ and ‘y’ is -10%.

The lacuna value for ‘width’ and ‘height’ is 120%.

Negative or zero values for ‘width’ or ‘height’ disable rendering of the element which referenced the filter.

Animatable: yes.

‘filterRes’

Defines the width and height of the intermediate images in pixels. If not provided, then the user agent will use reasonable values to produce a high-quality result on the output device.

Care should be taken when assigning a non-default value to this attribute. Too small of a value may result in unwanted pixelation in the result. Too large of a value may result in slow processing and large memory usage.

Non-integer values are truncated, i.e rounded to the closest integer value towards zero.

Negative or zero values disable rendering of the element which referenced the filter.

Animatable: yes.

Note that both of the two possible value for ‘filterUnits’ (i.e., objectBoundingBox and userSpaceOnUse) result in a filter region whose coordinate system has its X-axis and Y-axis each parallel to the X-axis and Y-axis, respectively, of the user coordinate system for the element to which the filter will be applied.

Sometimes implementers can achieve faster performance when the filter region can be mapped directly to device pixels; thus, for best performance on display devices, it is suggested that authors define their region such that the user agent can align the filter region pixel-for-pixel with the background. In particular, for best filter effects performance, avoid rotating or skewing the user coordinate system. Explicit values for attribute ‘filterRes’ can either help or harm performance. If ‘filterRes’ is smaller than the automatic (i.e., default) filter resolution, then filter effect might have faster performance (usually at the expense of quality). If ‘filterRes’ is larger than the automatic (i.e., default) filter resolution, then filter effects performance will usually be slower.

It is often necessary to provide padding space because the filter effect might impact bits slightly outside the tight-fitting bounding box on a given object. For these purposes, it is possible to provide negative percentage values for ‘x’, ‘y’ and percentages values greater than 100% for ‘width’, ‘height’. This, for example, is why the defaults for the filter effects region are x="-10%" y="-10%" width="120%" height="120%".

8. Filter primitives

8.1. Overview

This section describes the various filter primitives that can be assembled to achieve a particular filter effect.

Unless otherwise stated, all image filters operate on premultiplied RGBA samples. Filters which work more naturally on non-premultiplied data (<feColorMatrix>, <feCustom> and <feComponentTransfer>) will temporarily undo and redo premultiplication as specified. All raster effect filtering operations take 1 to N input RGBA images, additional attributes as parameters, and produce a single output RGBA image.

The RGBA result from each filter primitive will be clamped into the allowable ranges for colors and opacity values. Thus, for example, the result from a given filter primitive will have any negative color values or opacity values adjusted up to color/opacity of zero.

The color space in which a particular filter primitive performs its operations is determined by the value of property ‘color-interpolation-filters’ on the given filter primitive. A different property, ‘color-interpolation’ determines the color space for other color operations. Because these two properties have different initial values (‘color-interpolation-filters’ has an initial value of linearRGB whereas ‘color-interpolation’ has an initial value of ‘sRGB’), in some cases to achieve certain results (e.g., when coordinating gradient interpolation with a filtering operation) it will be necessary to explicitly set ‘color-interpolation’ to ‘linearRGB’ or ‘color-interpolation-filters’ to ‘sRGB’ on particular elements. Note that the examples below do not explicitly set either ‘color-interpolation’ or ‘color-interpolation-filters’, so the initial values for these properties apply to the examples.

Sometimes filter primitives result in undefined pixels. For example, filter primitive <feOffset> can shift an image down and to the right, leaving undefined pixels at the top and left. In these cases, the undefined pixels are set to transparent black.

8.2. Common attributes

The following attributes are available for most of the filter primitives:

8.3. Filter primitive subregion

Define filter primitive subregion for shorthands. E.g. the out bounds of the previous filter functions, extended by affected area of current filter function.

All filter primitives have attributes ‘x’, ‘y’, ‘width’ and ‘height’ which together identify a subregion which restricts calculation and rendering of the given filter primitive. The ‘x’, ‘y’, ‘width’ and ‘height’ attributes are defined according to the same rules as other filter primitives coordinate and length attributes and thus represent values in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.

‘x’, ‘y’, ‘width’ and ‘height’ default to the union (i.e., tightest fitting bounding box) of the subregions defined for all referenced nodes. If there are no referenced nodes (e.g., for <feImage> or <feTurbulence>), or one or more of the referenced nodes is a standard input (one of SourceGraphic, SourceAlpha, BackgroundImage, BackgroundAlpha, FillPaint or StrokePaint), or for <feTile> (which is special because its principal function is to replicate the referenced node in X and Y and thereby produce a usually larger result), the default subregion is 0%, 0%, 100%, 100%, where as a special-case the percentages are relative to the dimensions of the filter region, thus making the default filter primitive subregion equal to the filter region.

If the filter primitive subregion has a negative or zero width or height, the effect of the filter primitive is disabled.

The filter primitive subregion act as a hard clip clipping rectangle on both the filter primitive's input image(s) and the filter primitive result.

All intermediate offscreens are defined to not exceed the intersection of the filter primitive subregion with the filter region. The filter region and any of the filter primitive subregions are to be set up such that all offscreens are made big enough to accommodate any pixels which even partly intersect with either the filter region or the filter primitive subregions.

<feTile> references a previous filter primitive and then stitches the tiles together based on the filter primitive subregion of the referenced filter primitive in order to fill its own filter primitive subregion.

<svg width="400" height="400" xmlns="https://www.w3.org/2000/svg"> 
  <defs>
    <filter id="flood" x="0" y="0" width="100%" height="100%" primitiveUnits="objectBoundingBox">
       <feFlood x="25%" y="25%" width="50%" height="50%"
          flood-color="green" flood-opacity="0.75"/>
    </filter>
    <filter id="blend" primitiveUnits="objectBoundingBox">
       <feBlend x="25%" y="25%" width="50%" height="50%"
          in2="SourceGraphic" mode="multiply"/>
    </filter>
    <filter id="merge" primitiveUnits="objectBoundingBox">
       <feMerge x="25%" y="25%" width="50%" height="50%">
        <feMergeNode in="SourceGraphic"/>
        <feMergeNode in="FillPaint"/>
       </feMerge>
    </filter>
  </defs>
  
  <g fill="none" stroke="blue" stroke-width="4">
     <rect width="200" height="200"/>
     <line x2="200" y2="200"/>
     <line x1="200" y2="200"/>
  </g>
  <circle fill="green" filter="url(#flood)" cx="100" cy="100" r="90"/>
  <g transform="translate(200 0)">
    <g fill="none" stroke="blue" stroke-width="4">
       <rect width="200" height="200"/>
       <line x2="200" y2="200"/>
       <line x1="200" y2="200"/>
    </g>
    <circle fill="green" filter="url(#blend)" cx="100" cy="100" r="90"/>
  </g>
  
  <g transform="translate(0 200)">
    <g fill="none" stroke="blue" stroke-width="4">
       <rect width="200" height="200"/>
       <line x2="200" y2="200"/>
       <line x1="200" y2="200"/>
    </g>
    <circle fill="green" fill-opacity="0.5" filter="url(#merge)" cx="100" cy="100" r="90"/>
  </g>
</svg>

Example for subregions

View this example as SVG (SVG-enabled browsers only)

In the example above there are three rects that each have a cross and a circle in them. The circle element in each one has a different filter applied, but with the same filter primitive subregion. The filter output should be limited to the filter primitive subregion, so you should never see the circles themselves, just the rects that make up the filter primitive subregion.

• The upper left rect shows an <feFlood> with flood-opacity="75%" so the cross should be visible through the green rect in the middle.
• The lower left rect shows an <feMerge> that merges SourceGraphic with FillPaint. Since the circle has fill-opacity="0.5" it will also be transparent so that the cross is visible through the green rect in the middle.
• The upper right rect shows an <feBlend> that has mode="multiply". Since the circle in this case isn't transparent the result is totally opaque. The rect should be dark green and the cross should not be visible through it.

8.4. Filter primitive <feBlend>

This filter composites two objects together using commonly used imaging software blending modes. It performs a pixel-wise combination of two input images.

For all feBlend modes, the result opacity is computed as follows:

qr = 1 - (1-qa)*(1-qb)

For the compositing formulas below, the following definitions apply:

image A = in
image B = in2
cr = Result color (RGB) - premultiplied 
qa = Opacity value at a given pixel for image A 
qb = Opacity value at a given pixel for image B 
ca = Color (RGB) at a given pixel for image A - premultiplied 
cb = Color (RGB) at a given pixel for image B - premultiplied 

The following table provides the list of available image blending modes:

cr = (1 - qa) * cb + ca

cr = (1 - qa) * cb + (1 - qb) * ca + ca * cb

cr = cb + ca - ca * cb

cr = Min ((1 - qa) * cb + ca, (1 - qb) * ca + cb)

cr = Max ((1 - qa) * cb + ca, (1 - qb) * ca + cb)

The ‘normal’ blend mode is equivalent to operator="over" on the <feComposite> filter primitive, matches the blending method used by <feMerge> and matches the simple alpha compositing technique used in SVG for all compositing outside of filter effects.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="5cm" height="5cm" viewBox="0 0 500 500"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example feBlend - Examples of feBlend modes</title>
  <desc>Five text strings blended into a gradient,
        with one text string for each of the five feBlend modes.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="300" y2="0">
      <stop offset="0" stop-color="#000000" />
      <stop offset=".33" stop-color="#ffffff" />
      <stop offset=".67" stop-color="#ff0000" />
      <stop offset="1" stop-color="#808080" />
    </linearGradient>
    <filter id="Normal">
      <feBlend mode="normal" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Multiply">
      <feBlend mode="multiply" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Screen">
      <feBlend mode="screen" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Darken">
      <feBlend mode="darken" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Lighten">
      <feBlend mode="lighten" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="498" height="498"/>
  <g enable-background="new" >
    <rect x="100" y="20" width="300" height="460" fill="url(#MyGradient)" />
    <g font-family="Verdana" font-size="75" fill="#888888" fill-opacity=".6" >
      <text x="50" y="90" filter="url(#Normal)" >Normal</text>
      <text x="50" y="180" filter="url(#Multiply)" >Multiply</text>
      <text x="50" y="270" filter="url(#Screen)" >Screen</text>
      <text x="50" y="360" filter="url(#Darken)" >Darken</text>
      <text x="50" y="450" filter="url(#Lighten)" >Lighten</text>
    </g>
  </g>
</svg>

Example of feBlend

View this example as SVG (SVG-enabled browsers only)

8.5. Filter primitive <feColorMatrix>

This filter applies a matrix transformation: $\left[\begin{array}{c}R\text{'}\\ G\text{'}\\ B\text{'}\\ A\text{'}\\ 1\end{array}\right]=\left[\begin{array}{ccccc}{a}_{00}& a_{01}& a_{02}& a_{03}& a_{04}\\ a_{10}& a_{11}& a_{12}& a_{13}& a_{14}\\ a_{20}& a_{21}& a_{22}& a_{23}& a_{24}\\ a_{30}& a_{31}& a_{32}& a_{33}& a_{34}\\ 0& 0& 0& 0& 1\end{array}\right]\cdot \left[\begin{array}{c}R\\ G\\ B\\ A\\ 1\end{array}\right]$

on the RGBA color and alpha values of every pixel on the input graphics to produce a result with a new set of RGBA color and alpha values.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation.

These matrices often perform an identity mapping in the alpha channel. If that is the case, an implementation can avoid the costly undoing and redoing of the premultiplication for all pixels with A = 1.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="8cm" height="5cm" viewBox="0 0 800 500"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example feColorMatrix - Examples of feColorMatrix operations</title>
  <desc>Five text strings showing the effects of feColorMatrix: 
        an unfiltered text string acting as a reference, 
        use of the feColorMatrix matrix option to convert to grayscale,
        use of the feColorMatrix saturate option,
        use of the feColorMatrix hueRotate option,
        and use of the feColorMatrix luminanceToAlpha option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="500" y2="0">
      <stop offset="0" stop-color="#ff00ff" />
      <stop offset=".33" stop-color="#88ff88" />
      <stop offset=".67" stop-color="#2020ff" />
      <stop offset="1" stop-color="#d00000" />
    </linearGradient>
    <filter id="Matrix" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="matrix" in="SourceGraphic"
           values=".33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0"/>
    </filter>
    <filter id="Saturate40" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="saturate" in="SourceGraphic" values="0.4"/>
    </filter>
    <filter id="HueRotate90" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="hueRotate" in="SourceGraphic" values="90"/>
    </filter>
    <filter id="LuminanceToAlpha" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="luminanceToAlpha" in="SourceGraphic" result="a"/>
      <feComposite in="SourceGraphic" in2="a" operator="in" />
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="498"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="500" height="20" />
    <text x="100" y="90">Unfiltered</text>
    <text x="100" y="190" filter="url(#Matrix)" >Matrix</text>
    <text x="100" y="290" filter="url(#Saturate40)" >Saturate</text>
    <text x="100" y="390" filter="url(#HueRotate90)" >HueRotate</text>
    <text x="100" y="490" filter="url(#LuminanceToAlpha)" >Luminance</text>
  </g>
</svg>

Example of feColorMatrix

View this example as SVG (SVG-enabled browsers only)

8.6. Filter primitive <feComponentTransfer>

This filter primitive performs component-wise remapping of data as follows:

R' = feFuncR( R )
G' = feFuncG( G )
B' = feFuncB( B )
A' = feFuncA( A )

for every pixel. It allows operations like brightness adjustment, contrast adjustment, color balance or thresholding.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation. (Note that the undoing and redoing of the premultiplication can be avoided if <feFuncA> is the identity transform and all alpha values on the source graphic are set to 1.)

The child elements of a <feComponentTransfer> element specify the transfer functions for the four channels:

• <feFuncR> — transfer function for the red component of the input graphic
• <feFuncG> — transfer function for the green component of the input graphic
• <feFuncB> — transfer function for the blue component of the input graphic
• <feFuncA> — transfer function for the alpha component of the input graphic

The following rules apply to the processing of the <feComponentTransfer> element:

• If more than one transfer function element of the same kind is specified, the last occurrence is to be used.
• If any of the transfer function elements are unspecified, the <feComponentTransfer> must be processed as if those transfer function elements were specified with their ‘type’ attributes set to ‘identity’.

Name:	feFuncR
Categories:	Transfer function element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ transfer function element attributes — ‘type’, ‘tableValues’, ‘slope’, ‘intercept’, ‘amplitude’, ‘exponent’, ‘offset’
DOM Interfaces:	SVGFEFuncRElement

Name:	feFuncG
Categories:	Transfer function element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ transfer function element attributes — ‘type’, ‘tableValues’, ‘slope’, ‘intercept’, ‘amplitude’, ‘exponent’, ‘offset’
DOM Interfaces:	SVGFEFuncGElement

Name:	feFuncB
Categories:	Transfer function element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ transfer function element attributes — ‘type’, ‘tableValues’, ‘slope’, ‘intercept’, ‘amplitude’, ‘exponent’, ‘offset’
DOM Interfaces:	SVGFEFuncBElement

Name:	feFuncA
Categories:	Transfer function element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ transfer function element attributes — ‘type’, ‘tableValues’, ‘slope’, ‘intercept’, ‘amplitude’, ‘exponent’, ‘offset’
DOM Interfaces:	SVGFEFuncAElement

The attributes below are the transfer function element attributes, which apply to the transfer function elements.

Attribute definitions:

type = "identity | table | discrete | linear | gamma"

Indicates the type of component transfer function. The type of function determines the applicability of the other attributes.

In the following, C is the initial component (e.g., <feFuncR>), C' is the remapped component; both in the closed interval [0,1].

• For ‘identity’:

  C' = C

• For ‘table’, the function is defined by linear interpolation between values given in the attribute ‘tableValues’. The table has n+1 values (i.e., v₀ to v_n) specifying the start and end values for n evenly sized interpolation regions. Interpolations use the following formula:

  For a value C < 1 find k such that:

  k/n <= C < (k+1)/n

  The result C' is given by:

  C' = v_k + (C - k/n)*n * (v_k+1 - v_k)

  If C = 1 then:

  C' = v_n.

• For ‘discrete’, the function is defined by the step function given in the attribute ‘tableValues’, which provides a list of n values (i.e., v₀ to v_n-1) in order to identify a step function consisting of n steps. The step function is defined by the following formula:

  For a value C < 1 find k such that:

  k/n <= C < (k+1)/n

  The result C' is given by:

  C' = v_k

  If C = 1 then:

  C' = v_n-1.

• For ‘linear’, the function is defined by the following linear equation:

  C' = slope * C + intercept

• For ‘gamma’, the function is defined by the following exponential function:

  C' = amplitude * pow(C, exponent) + offset

Animatable: yes.

tableValues = "(list of <number>s)"

When type="table", the list of <number> s v0,v1,...vn, separated by white space and/or a comma, which define the lookup table. An empty list results in an identity transfer function. If the attribute is not specified, then the effect is as if an empty list were provided.
Animatable: yes.

slope = "<number>"

When type="linear", the slope of the linear function.
The lacuna value for ‘slope’ is 1.
Animatable: yes.

intercept = "<number>"

When type="linear", the intercept of the linear function.
The lacuna value for ‘intercept’ is 0.
Animatable: yes.

amplitude = "<number>"

When type="gamma", the amplitude of the gamma function.
The lacuna value for ‘amplitude’ is 1.
Animatable: yes.

exponent = "<number>"

When type="gamma", the exponent of the gamma function.
The lacuna value for ‘exponent’ is 1.
Animatable: yes.

offset = "<number>"

When type="gamma", the offset of the gamma function.
The lacuna value for ‘offset’ is 0.
Animatable: yes.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="8cm" height="4cm" viewBox="0 0 800 400"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example feComponentTransfer - Examples of feComponentTransfer operations</title>
  <desc>Four text strings showing the effects of feComponentTransfer: 
        an identity function acting as a reference, 
        use of the feComponentTransfer table option,
        use of the feComponentTransfer linear option,
        and use of the feComponentTransfer gamma option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="600" y2="0">
      <stop offset="0" stop-color="#ff0000" />
      <stop offset=".33" stop-color="#00ff00" />
      <stop offset=".67" stop-color="#0000ff" />
      <stop offset="1" stop-color="#000000" />
    </linearGradient>
    <filter id="Identity" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="identity"/>
        <feFuncG type="identity"/>
        <feFuncB type="identity"/>
        <feFuncA type="identity"/>
      </feComponentTransfer>
    </filter>
    <filter id="Table" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="table" tableValues="0 0 1 1"/>
        <feFuncG type="table" tableValues="1 1 0 0"/>
        <feFuncB type="table" tableValues="0 1 1 0"/>
      </feComponentTransfer>
    </filter>
    <filter id="Linear" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="linear" slope=".5" intercept=".25"/>
        <feFuncG type="linear" slope=".5" intercept="0"/>
        <feFuncB type="linear" slope=".5" intercept=".5"/>
      </feComponentTransfer>
    </filter>
    <filter id="Gamma" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="gamma" amplitude="2" exponent="5" offset="0"/>
        <feFuncG type="gamma" amplitude="2" exponent="3" offset="0"/>
        <feFuncB type="gamma" amplitude="2" exponent="1" offset="0"/>
      </feComponentTransfer>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="398"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="600" height="20" />
    <text x="100" y="90">Identity</text>
    <text x="100" y="190" filter="url(#Table)" >TableLookup</text>
    <text x="100" y="290" filter="url(#Linear)" >LinearFunc</text>
    <text x="100" y="390" filter="url(#Gamma)" >GammaFunc</text>
  </g>
</svg>

Example for feComponentTransfer

View this example as SVG (SVG-enabled browsers only)

8.7. Filter primitive <feComposite>

Name:	feComposite
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘in2’ ‘operator’ ‘k1’ ‘k2’ ‘k3’ ‘k4’
DOM Interfaces:	SVGFECompositeElement

This filter performs the combination of the two input images pixel-wise in image space using one of the Porter-Duff [PORTERDUFF] compositing operations: over, in, atop, out, xor [COMPOSITING]. Additionally, a component-wise arithmetic operation (with the result clamped between [0..1]) can be applied.

The arithmetic operation is useful for combining the output from the <feDiffuseLighting> and <feSpecularLighting> filters with texture data. It is also useful for implementing dissolve. If the arithmetic operation is chosen, each result pixel is computed using the following formula:

result = k1*i1*i2 + k2*i1 + k3*i2 + k4

where:

• i1 and i2 indicate the corresponding pixel channel values of the input image, which map to ‘in’ and ‘in2’ respectively
• k1, k2, k3 and k4 indicate the values of the attributes with the same name

For this filter primitive, the extent of the resulting image might grow as described in the section that describes the filter primitive subregion.

Attribute definitions:

operator = "over | in | out | atop | xor | arithmetic"

The compositing operation that is to be performed. All of the operator types except arithmetic match the corresponding operation as described in [PORTERDUFF]. The arithmetic operator is described above. The lacuna value for ‘operator’ is over.
Animatable: yes.

k1 = "<number>"

Only applicable if operator="arithmetic".
The lacuna value for ‘k1’ is 0.
Animatable: yes.

k2 = "<number>"

Only applicable if operator="arithmetic".
The lacuna value for ‘k2’ is 0.
Animatable: yes.

k3 = "<number>"

Only applicable if operator="arithmetic".
The lacuna value for ‘k3’ is 0.
Animatable: yes.

k4 = "<number>"

Only applicable if operator="arithmetic".
The lacuna value for ‘k4’ is 0.
Animatable: yes.

in2 = "(see in attribute)"

The second input image to the compositing operation. This attribute can take on the same values as the in attribute.
Animatable: yes.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="330" height="195" viewBox="0 0 1100 650" version="1.1"
     xmlns="https://www.w3.org/2000/svg" xmlns:xlink="https://www.w3.org/1999/xlink">
  <title>Example feComposite - Examples of feComposite operations</title>
  <desc>Four rows of six pairs of overlapping triangles depicting
        the six different feComposite operators under different
        opacity values and different clearing of the background.</desc>
  <defs>
    <desc>Define two sets of six filters for each of the six compositing operators.
          The first set wipes out the background image by flooding with opaque white.
          The second set does not wipe out the background, with the result
          that the background sometimes shines through and is other cases
          is blended into itself (i.e., "double-counting").</desc>
    <filter id="overFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="inFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="outFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="atopFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="xorFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="arithmeticFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="overNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
    </filter>
    <filter id="inNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
    </filter>
    <filter id="outNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
    </filter>
    <filter id="atopNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
    </filter>
    <filter id="xorNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
    </filter>
    <filter id="arithmeticNoFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
    </filter>
    <path id="Blue100" d="M 0 0 L 100 0 L 100 100 z" fill="#00ffff" />
    <path id="Red100" d="M 0 0 L 0 100 L 100 0 z" fill="#ff00ff" />
    <path id="Blue50" d="M 0 125 L 100 125 L 100 225 z" fill="#00ffff" fill-opacity=".5" />
    <path id="Red50" d="M 0 125 L 0 225 L 100 125 z" fill="#ff00ff" fill-opacity=".5" />
    <g id="TwoBlueTriangles">
      <use xlink:href="#Blue100"/>
      <use xlink:href="#Blue50"/>
    </g>
    <g id="BlueTriangles">
      <use transform="translate(275,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(400,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(525,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(650,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(775,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(900,25)" xlink:href="#TwoBlueTriangles"/>
    </g>
  </defs>
  <rect fill="none" stroke="blue" x="1" y="1" width="1098" height="648"/>
  <g font-family="Verdana" font-size="40" shape-rendering="crispEdges">
    <desc>Render the examples using the filters that draw on top of
          an opaque white surface, thus obliterating the background.</desc>
    <g enable-background="new">
      <text x="15" y="75">opacity 1.0</text>
      <text x="15" y="115" font-size="27">(with feFlood)</text>
      <text x="15" y="200">opacity 0.5</text>
      <text x="15" y="240" font-size="27">(with feFlood)</text>
      <use xlink:href="#BlueTriangles"/>
      <g transform="translate(275,25)">
        <use xlink:href="#Red100" filter="url(#overFlood)" />
        <use xlink:href="#Red50" filter="url(#overFlood)" />
        <text x="5" y="275">over</text>
      </g>
      <g transform="translate(400,25)">
        <use xlink:href="#Red100" filter="url(#inFlood)" />
        <use xlink:href="#Red50" filter="url(#inFlood)" />
        <text x="35" y="275">in</text>
      </g>
      <g transform="translate(525,25)">
        <use xlink:href="#Red100" filter="url(#outFlood)" />
        <use xlink:href="#Red50" filter="url(#outFlood)" />
        <text x="15" y="275">out</text>
      </g>
      <g transform="translate(650,25)">
        <use xlink:href="#Red100" filter="url(#atopFlood)" />
        <use xlink:href="#Red50" filter="url(#atopFlood)" />
        <text x="10" y="275">atop</text>
      </g>
      <g transform="translate(775,25)">
        <use xlink:href="#Red100" filter="url(#xorFlood)" />
        <use xlink:href="#Red50" filter="url(#xorFlood)" />
        <text x="15" y="275">xor</text>
      </g>
      <g transform="translate(900,25)">
        <use xlink:href="#Red100" filter="url(#arithmeticFlood)" />
        <use xlink:href="#Red50" filter="url(#arithmeticFlood)" />
        <text x="-25" y="275">arithmetic</text>
      </g>
    </g>
    <g transform="translate(0,325)" enable-background="new">
    <desc>Render the examples using the filters that do not obliterate
          the background, thus sometimes causing the background to continue
          to appear in some cases, and in other cases the background
          image blends into itself ("double-counting").</desc>
      <text x="15" y="75">opacity 1.0</text>
      <text x="15" y="115" font-size="27">(without feFlood)</text>
      <text x="15" y="200">opacity 0.5</text>
      <text x="15" y="240" font-size="27">(without feFlood)</text>
      <use xlink:href="#BlueTriangles"/>
      <g transform="translate(275,25)">
        <use xlink:href="#Red100" filter="url(#overNoFlood)" />
        <use xlink:href="#Red50" filter="url(#overNoFlood)" />
        <text x="5" y="275">over</text>
      </g>
      <g transform="translate(400,25)">
        <use xlink:href="#Red100" filter="url(#inNoFlood)" />
        <use xlink:href="#Red50" filter="url(#inNoFlood)" />
        <text x="35" y="275">in</text>
      </g>
      <g transform="translate(525,25)">
        <use xlink:href="#Red100" filter="url(#outNoFlood)" />
        <use xlink:href="#Red50" filter="url(#outNoFlood)" />
        <text x="15" y="275">out</text>
      </g>
      <g transform="translate(650,25)">
        <use xlink:href="#Red100" filter="url(#atopNoFlood)" />
        <use xlink:href="#Red50" filter="url(#atopNoFlood)" />
        <text x="10" y="275">atop</text>
      </g>
      <g transform="translate(775,25)">
        <use xlink:href="#Red100" filter="url(#xorNoFlood)" />
        <use xlink:href="#Red50" filter="url(#xorNoFlood)" />
        <text x="15" y="275">xor</text>
      </g>
      <g transform="translate(900,25)">
        <use xlink:href="#Red100" filter="url(#arithmeticNoFlood)" />
        <use xlink:href="#Red50" filter="url(#arithmeticNoFlood)" />
        <text x="-25" y="275">arithmetic</text>
      </g>
    </g>
  </g>
</svg>

Example of feComposite

View this example as SVG (SVG-enabled browsers only)

8.8. Filter primitive <feConvolveMatrix>

Name:	feConvolveMatrix
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘order’ ‘kernelMatrix’ ‘divisor’ ‘bias’ ‘targetX’ ‘targetY’ ‘edgeMode’ ‘kernelUnitLength’ ‘preserveAlpha’
DOM Interfaces:	SVGFEConvolveMatrixElement

feConvolveMatrix applies a matrix convolution filter effect. A convolution combines pixels in the input image with neighboring pixels to produce a resulting image. A wide variety of imaging operations can be achieved through convolutions, including blurring, edge detection, sharpening, embossing and beveling.

A matrix convolution is based on an n-by-m matrix (the convolution kernel) which describes how a given pixel value in the input image is combined with its neighboring pixel values to produce a resulting pixel value. Each result pixel is determined by applying the kernel matrix to the corresponding source pixel and its neighboring pixels. The basic convolution formula which is applied to each color value for a given pixel is:

${\mathrm{color}}_{X,Y}=\frac{\sum _{i=0}^{\mathrm{orderY}-1}\sum _{j=0}^{\mathrm{orderX}-1}{\mathrm{source}}_{x-\mathrm{targetX}+j,y-\mathit{targetY}+i}\cdot {\mathrm{kernalMatrix}}_{\mathrm{orderX}-j-\mathrm{1,}\mathrm{orderY}-i-1}}{\mathrm{divisor}}+\mathrm{bias}\cdot {\mathrm{alpha}}_{x,y}$

where "orderX" and "orderY" represent the X and Y values for the ‘order’ attribute, "targetX" represents the value of the ‘targetX’ attribute, "targetY" represents the value of the ‘targetY’ attribute, "kernelMatrix" represents the value of the ‘kernelMatrix’ attribute, "divisor" represents the value of the ‘divisor’ attribute, and "bias" represents the value of the ‘bias’ attribute.

Note in the above formulas that the values in the kernel matrix are applied such that the kernel matrix is rotated 180 degrees relative to the source and destination images in order to match convolution theory as described in many computer graphics textbooks.

To illustrate, suppose you have a input image which is 5 pixels by 5 pixels, whose color values for one of the color channels are as follows:

$\left[\begin{array}{ccccc}0& 20& 40& 235& 235\\ 100& 120& 140& 235& 235\\ 200& 220& 240& 235& 235\\ 255& 255& 255& 255& 255\\ 255& 255& 255& 255& 255\end{array}\right]$

and you define a 3-by-3 convolution kernel as follows:

$\left[\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\\ 7& 8& 9\end{array}\right]$

Let's focus on the color value at the second row and second column of the image (source pixel value is 120). Assuming the simplest case (where the input image's pixel grid aligns perfectly with the kernel's pixel grid) and assuming default values for attributes ‘divisor’, ‘targetX’ and ‘targetY’, then resulting color value will be:

${\mathrm{resultChannel}}_{\mathrm{2,2}}=\frac{9\cdot 0+8\cdot 20+7\cdot 40+6\cdot 100+5\cdot 120+4\cdot 140+3\cdot 200+2\cdot 220+1\cdot 240}{9+8+7+6+5+4+3+2+1}$

Because they operate on pixels, matrix convolutions are inherently resolution-dependent. To make <feConvolveMatrix> produce resolution-independent results, an explicit value should be provided for either the ‘filterRes’ attribute on the <filter> element and/or attribute ‘kernelUnitLength’.

‘kernelUnitLength’, in combination with the other attributes, defines an implicit pixel grid in the filter effects coordinate system (i.e., the coordinate system established by the ‘primitiveUnits’ attribute). If the pixel grid established by ‘kernelUnitLength’ is not scaled to match the pixel grid established by attribute ‘filterRes’ (implicitly or explicitly), then the input image will be temporarily rescaled to match its pixels with ‘kernelUnitLength’. The convolution happens on the resampled image. After applying the convolution, the image is resampled back to the original resolution.

When the image must be resampled to match the coordinate system defined by ‘kernelUnitLength’ prior to convolution, or resampled to match the device coordinate system after convolution, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the ‘image-rendering’ property setting. Note that implementations might choose approaches that minimize or eliminate resampling when not necessary to produce proper results, such as when the document is zoomed out such that ‘kernelUnitLength’ is considerably smaller than a device pixel.

Attribute definitions:

order = "<number-optional-number>"

Indicates the number of cells in each dimension for ‘kernelMatrix’. The values provided must be <integer> s greater than zero. Values that are not integers will be truncated, i.e. rounded to the closest integer value towards zero. The first number, <orderX>, indicates the number of columns in the matrix. The second number, <orderY>, indicates the number of rows in the matrix. If <orderY> is not provided, it defaults to <orderX>.
It is recommended that only small values (e.g., 3) be used; higher values may result in very high CPU overhead and usually do not produce results that justify the impact on performance.
The lacuna value for ‘order’ is 3.
Animatable: yes.

kernelMatrix = "<list of numbers>"

The list of <number> s that make up the kernel matrix for the convolution. Values are separated by space characters and/or a comma. The number of entries in the list must equal <orderX> times <orderY>.
Animatable: yes.

divisor = "<number>"

After applying the kernelMatrix to the input image to yield a number, that number is divided by ‘divisor’ to yield the final destination color value. A divisor that is the sum of all the matrix values tends to have an evening effect on the overall color intensity of the result. If the specified divisor is zero then the default value will be used instead. The lacuna value is the sum of all values in kernelMatrix, with the exception that if the sum is zero, then the divisor is set to 1.
Animatable: yes.

bias = "<number>"

After applying the kernelMatrix to the input image to yield a number and applying the ‘divisor’, the ‘bias’ attribute is added to each component. One application of ‘bias’ is when it is desirable to have .5 gray value be the zero response of the filter. The bias property shifts the range of the filter. This allows representation of values that would otherwise be clamped to 0 or 1.
The lacuna value for ‘bias’ is 0.
Animatable: yes.

targetX = "<integer>"

Determines the positioning in X of the convolution matrix relative to a given target pixel in the input image. The leftmost column of the matrix is column number zero. The value must be such that: 0 <= targetX < orderX. By default, the convolution matrix is centered in X over each pixel of the input image (i.e., targetX = floor ( orderX / 2 )).
Animatable: yes.

targetY = "<integer>"

Determines the positioning in Y of the convolution matrix relative to a given target pixel in the input image. The topmost row of the matrix is row number zero. The value must be such that: 0 <= targetY < orderY. By default, the convolution matrix is centered in Y over each pixel of the input image (i.e., targetY = floor ( orderY / 2 )).
Animatable: yes.

edgeMode = "duplicate | wrap | none"

Determines how to extend the input image as necessary with color values so that the matrix operations can be applied when the kernel is positioned at or near the edge of the input image.

"duplicate" indicates that the input image is extended along each of its borders as necessary by duplicating the color values at the given edge of the input image.

Original N-by-M image, where m=M-1 and n=N-1:

$\left[\begin{array}{ccccc}11& 12& \text{.}\text{.}\text{.}& 1m& 1M\\ 21& 22& \text{.}\text{.}\text{.}& 2m& 2M\\ \text{.}\text{.}\text{.}& \text{.}\text{.}\text{.}& \text{.}\text{.}\text{.}& \text{.}\text{.}\text{.}& \text{.}\text{.}\text{.}\\ n1& n2& \text{.}\text{.}\text{.}& \mathrm{nm}& \mathrm{nM}\\ N1& N2& \text{.}\text{.}\text{.}& \mathrm{Nm}& \mathrm{NM}\end{array}\right]$

Extended by two pixels using "duplicate":

$\left[\begin{array}{ccccccccc}11& 11& 11& 12& \dots & 1m& 1M& 1M& 1M\\ 11& 11& 11& 12& \dots & 1m& 1M& 1M& 1M\\ 11& 11& 11& 12& \dots & 1m& 1M& 1M& 1M\\ 21& 21& 21& 22& \dots & 2m& 2M& 2M& 2M\\ \dots & \dots & \dots & \dots & \dots & \dots & \dots & \dots & \dots \\ n1& n1& n1& n2& \dots & \mathrm{nm}& \mathrm{nM}& \mathrm{nM}& \mathrm{nM}\\ N1& N1& N1& N2& \dots & \mathrm{Nm}& \mathrm{NM}& \mathrm{NM}& \mathrm{NM}\\ N1& N1& N1& N2& \dots & \mathrm{Nm}& \mathrm{NM}& \mathrm{NM}& \mathrm{NM}\\ N1& N1& N1& N2& \dots & \mathrm{Nm}& \mathrm{NM}& \mathrm{NM}& \mathrm{NM}\end{array}\right]$

"wrap" indicates that the input image is extended by taking the color values from the opposite edge of the image.

Extended by two pixels using "wrap":

$\left[\begin{array}{ccccccccc}\mathit{nm}& \mathit{nM}& \mathit{n1}& \mathit{n2}& \dots & \mathit{nm}& \mathit{nM}& \mathit{n1}& \mathit{n2}\\ \mathit{Nm}& \mathit{NM}& \mathit{N1}& \mathit{N2}& \dots & \mathit{Nm}& \mathit{NM}& \mathit{N1}& \mathit{N2}\\ \mathrm{1m}& \mathrm{1M}& 11& 12& \dots & \mathrm{1m}& \mathrm{1M}& 11& 12\\ \mathrm{2m}& \mathrm{2M}& 21& 22& \dots & \mathrm{2m}& \mathrm{2M}& 21& 22\\ \dots & \dots & \dots & \dots & \dots & \dots & \dots & \dots & \dots \\ \mathit{nm}& \mathit{nM}& \mathit{n1}& \mathit{n2}& \dots & \mathit{nm}& \mathit{nM}& \mathit{n1}& \mathit{n2}\\ \mathit{Nm}& \mathit{NM}& \mathit{N1}& \mathit{N2}& \dots & \mathit{Nm}& \mathit{NM}& \mathit{N1}& \mathit{N2}\\ \mathrm{1m}& \mathrm{1M}& 11& 12& \dots & \mathrm{1m}& \mathrm{1M}& 11& 12\\ \mathrm{2m}& \mathrm{2M}& 21& 22& \dots & \mathrm{2m}& \mathrm{2M}& 21& 22\end{array}\right]$

The value none indicates that the input image is extended with pixel values of zero for R, G, B and A.

The lacuna value for ‘edgeMode’ is duplicate.

Animatable: yes.

kernelUnitLength = "<number-optional-number>"

The first number is the <dx> value. The second number is the <dy> value. If the <dy> value is not specified, it defaults to the same value as <dx>. Indicates the intended distance in current filter units (i.e., units as determined by the value of attribute ‘primitiveUnits’) between successive columns and rows, respectively, in the ‘kernelMatrix’. By specifying value(s) for ‘kernelUnitLength’, the kernel becomes defined in a scalable, abstract coordinate system. If ‘kernelUnitLength’ is not specified, the default value is one pixel in the offscreen bitmap, which is a pixel-based coordinate system, and thus potentially not scalable. For some level of consistency across display media and user agents, it is necessary that a value be provided for at least one of ‘filterRes’ and ‘kernelUnitLength’. In some implementations, the most consistent results and the fastest performance will be achieved if the pixel grid of the temporary offscreen images aligns with the pixel grid of the kernel.
If a negative or zero value is specified the default value will be used instead.
Animatable: yes.

preserveAlpha = "false | true"

A value of false indicates that the convolution will apply to all channels, including the alpha channel. In this case the ALPHAX,Y of the convolution formula for a given pixel is:

ALPHA_X,Y = ( 
              SUM _{I=0 to [‘orderY’-1]} { 
                SUM _{J=0 to [‘orderX’-1]} { 
                  SOURCE _{X-‘targetX’+J, Y-‘targetY’+I} *  ‘kernelMatrix’_{‘orderX’-J-1,  ‘orderY’-I-1} 
                } 
              } 
            ) /  ‘divisor’ +  ‘bias’ 

A value of true indicates that the convolution will only apply to the color channels. In this case, the filter will temporarily unpremultiply the color component values, apply the kernel, and then re-premultiply at the end. In this case the ALPHAX,Y of the convolution formula for a given pixel is:

ALPHA_X,Y = SOURCE_X,Y

The lacuna value for ‘preserveAlpha’ is false.
Animatable: yes.

8.9. Filter primitive <feCustom>

Name:	feCustom
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set> <feCustomParam> <feCustomSource>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘geometry’
DOM Interfaces:	SVGFECustomElement

Attribute definitions:

geometry = "grid(<integer>{0,2} [ detached | attached ]?"

See the ‘geometry’ descriptor.
Animatable: yes.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are converted into non-premultiplied color values for this operation.

Each ‘feCustom’ element can have any number of ‘feCustomSource’ subelements. Each ‘feCustomSource’ references one resource.

Name:	feCustomSource
Categories:	None.
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘src’ ‘format’
DOM Interfaces:	SVGFECustomSourceElement

Attribute definitions:

src = "<string>"

An Functional IRI reference to an resource which defines the custom filter.
Animatable: yes.

format = "<string>"

The format of the resource referenced by the ‘src’ attribute.
Animatable: yes.

Each ‘feCustom’ element can have any number of ‘feCustomParam’ subelements. Each ‘feCustomParam’ node passes one parameter.

Name:	feCustomParam
Categories:	None.
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘ident’ ‘type’ ‘values’ ‘color’ ‘texture’ ‘transform’
DOM Interfaces:	SVGFECustomParamElement

Attribute definitions:

ident = "<string>"

Indicates the parameter name to the shaders.
Animatable: yes.

type = "number | array | vec2 | vec3 | vec4 | mat2 | mat3 | mat4 | color | image | transform"

Indicates the type of the parameter passed to the shaders. For the types ‘number’, ‘array’, ‘vec2’, ‘vec3’, ‘vec4’, ‘mat2’, ‘mat3’ and ‘mat4’, the ‘values’ attribute passes the values to the shader. For all other types, the attributes with the same name pass the parameter to the shader. The lacuna value for ‘type’ is number.
Animatable: yes.

values = "list of <number>s"

The contents of values depends on the value of attribute type:

• For type="number", values is a single real number value.
• For type="array", values is a list of at least one real number value.
• For type="vec2", values is a list of two real number values. The value list is interpreted as a vertical list, where the first entry equals the parameter on the top of the vector.
• For type="vec3", values is a list of three real number values. The value list is interpreted as a vertical list, where the first entry equals the parameter on the top of the vector.
• For type="vec4", values is a list of four real number values. The value list is interpreted as a vertical list, where the first entry equals the parameter on the top of the vector.
• For type="mat2", values is a list of four real number values. The list specifies a 2x2 homogeneous matrix in column-major order.
• For type="mat3", values is a list of nine real number values. The list specifies a 3x3 homogeneous matrix in column-major order.
• For type="mat4", values is a list of 16 real number values. The list specifies a 4x4 homogeneous matrix in column-major order.

If the attribute is not specified, then the default behavior depends on the value of attribute type. If type is ‘mat2’, ‘mat3’ or ‘mat4’, then this attribute defaults to the identity matrix. If type is ‘number’ or ‘array’, then this attribute defaults to the value 0. If type is ‘vec2’, ‘vec3’ or ‘vec4’, then this attribute defaults to a number list with values of 0. The length of the number list depends on the size of the specified vector.

Animatable: yes.

color = "<color>"

Indicates that a color value is passed as parameter to the shaders.
Animatable: yes.

image = "<URI>"

Indicates that a image is passed as parameter to the shaders.
Animatable: yes.

transform = "<transform-list>"

Indicates that a list of transform functions is passed as parameter to the shaders.
Animatable: yes.

8.10. Filter primitive <feDiffuseLighting>

Name:	feDiffuseLighting
Categories:	Filter primitive element
Content model:	Any number of descriptive elements and exactly one light source element, in any order.
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘surfaceScale’ ‘diffuseConstant’ ‘kernelUnitLength’
DOM Interfaces:	SVGFEDiffuseLightingElement

This filter primitive lights an image using the alpha channel as a bump map. The resulting image is an RGBA opaque image based on the light color with alpha = 1.0 everywhere. The lighting calculation follows the standard diffuse component of the Phong lighting model. The resulting image depends on the light color, light position and surface geometry of the input bump map.

The light map produced by this filter primitive can be combined with a texture image using the multiply term of the arithmetic <feComposite> compositing method. Multiple light sources can be simulated by adding several of these light maps together before applying it to the texture image.

The formulas below make use of 3x3 filters. Because they operate on pixels, such filters are inherently resolution-dependent. To make <feDiffuseLighting> produce resolution-independent results, an explicit value should be provided for either the ‘filterRes’ attribute on the <filter> element and/or attribute ‘kernelUnitLength’.

‘kernelUnitLength’, in combination with the other attributes, defines an implicit pixel grid in the filter effects coordinate system (i.e., the coordinate system established by the ‘primitiveUnits’ attribute). If the pixel grid established by ‘kernelUnitLength’ is not scaled to match the pixel grid established by attribute ‘filterRes’ (implicitly or explicitly), then the input image will be temporarily rescaled to match its pixels with ‘kernelUnitLength’. The 3x3 filters are applied to the resampled image. After applying the filter, the image is resampled back to its original resolution.

When the image must be resampled, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the ‘image-rendering’ property setting. Note that implementations might choose approaches that minimize or eliminate resampling when not necessary to produce proper results, such as when the document is zoomed out such that ‘kernelUnitLength’ is considerably smaller than a device pixel.

For the formulas that follow, the Norm(Ax,Ay,Az) function is defined as:

Consider making this into mathml

Norm(A_x,A_y,A_z) = sqrt(A_x^2+A_y^2+A_z^2)

The resulting RGBA image is computed as follows:

D_r = k_d * N.L * L_r
D_g = k_d * N.L * L_g
D_b = k_d * N.L * L_b
D_a = 1.0

where

k_d = diffuse lighting constant
N = surface normal unit vector, a function of x and y
L = unit vector pointing from surface to light, a function of x and y in the point and spot light cases
L_r,L_g,L_b = RGB components of light, a function of x and y in the spot light case

N is a function of x and y and depends on the surface gradient as follows:

The surface described by the input alpha image I(x,y) is:

Z (x,y) = surfaceScale * I(x,y)

Surface normal is calculated using the Sobel gradient 3x3 filter. Different filter kernels are used depending on whether the given pixel is on the interior or an edge. For each case, the formula is:

N_x (x,y) = - surfaceScale * FACTOR_x *
           (K_x(0,0)*I(x-dx,y-dy) + K_x(1,0)*I(x,y-dy) + K_x(2,0)*I(x+dx,y-dy) +
            K_x(0,1)*I(x-dx,y)    + K_x(1,1)*I(x,y)    + K_x(2,1)*I(x+dx,y)    +
            K_x(0,2)*I(x-dx,y+dy) + K_x(1,2)*I(x,y+dy) + K_x(2,2)*I(x+dx,y+dy))
N_y (x,y) = - surfaceScale * FACTOR_y *
           (K_y(0,0)*I(x-dx,y-dy) + K_y(1,0)*I(x,y-dy) + K_y(2,0)*I(x+dx,y-dy) +
            K_y(0,1)*I(x-dx,y)    + K_y(1,1)*I(x,y)    + K_y(2,1)*I(x+dx,y)    +
            K_y(0,2)*I(x-dx,y+dy) + K_y(1,2)*I(x,y+dy) + K_y(2,2)*I(x+dx,y+dy))
N_z (x,y) = 1.0

N = (N_x, N_y, N_z) / Norm((N_x,N_y,N_z))

In these formulas, the dx and dy values (e.g., I(x-dx,y-dy)), represent deltas relative to a given (x,y) position for the purpose of estimating the slope of the surface at that point. These deltas are determined by the value (explicit or implicit) of attribute ‘kernelUnitLength’.

Top/left corner: FACTORx=2/(3*dx) Kx =     |  0  0  0 |     |  0 -2  2 |     |  0 -1  1 | FACTORy=2/(3*dy) Ky =       |  0  0  0 |     |  0 -2 -1 |     |  0  2  1 |	Top row: FACTORx=1/(3*dx) Kx =     |  0  0  0 |     | -2  0  2 |     | -1  0  1 | FACTORy=1/(2*dy) Ky =       |  0  0  0 |     | -1 -2 -1 |     |  1  2  1 |	Top/right corner: FACTORx=2/(3*dx) Kx =     |  0  0  0 |     | -2  2  0 |     | -1  1  0 | FACTORy=2/(3*dy) Ky =       |  0  0  0 |     | -1 -2  0 |     |  1  2  0 |
Left column: FACTORx=1/(2*dx) Kx =     | 0 -1  1 |     | 0 -2  2 |     | 0 -1  1 | FACTORy=1/(3*dy) Ky =       |  0 -2 -1 |     |  0  0  0 |     |  0  2  1 |	Interior pixels: FACTORx=1/(4*dx) Kx =     | -1  0  1 |     | -2  0  2 |     | -1  0  1 | FACTORy=1/(4*dy) Ky =       | -1 -2 -1 |     |  0  0  0 |     |  1  2  1 |	Right column: FACTORx=1/(2*dx) Kx =     | -1  1  0|     | -2  2  0|     | -1  1  0| FACTORy=1/(3*dy) Ky =       | -1 -2  0 |     |  0  0  0 |     |  1  2  0 |
Bottom/left corner: FACTORx=2/(3*dx) Kx =     | 0 -1  1 |     | 0 -2  2 |     | 0  0  0 | FACTORy=2/(3*dy) Ky =       |  0 -2 -1 |     |  0  2  1 |     |  0  0  0 |	Bottom row: FACTORx=1/(3*dx) Kx =     | -1  0  1 |     | -2  0  2 |     |  0  0  0 | FACTORy=1/(2*dy) Ky =       | -1 -2 -1 |     |  1  2  1 |     |  0  0  0 |	Bottom/right corner: FACTORx=2/(3*dx) Kx =     | -1  1  0 |     | -2  2  0 |     |  0  0  0 | FACTORy=2/(3*dy) Ky =       | -1 -2  0 |     |  1  2  0 |     |  0  0  0 |

L, the unit vector from the image sample to the light, is calculated as follows:

For Infinite light sources it is constant:

L_x = cos(azimuth)*cos(elevation)
L_y = sin(azimuth)*cos(elevation)
L_z = sin(elevation)

For Point and spot lights it is a function of position:

L_x = Light_x - x
L_y = Light_y - y
L_z = Light_z - Z(x,y)

L = (L_x, L_y, L_z) / Norm(L_x, L_y, L_z)

where Light_x, Light_y, and Light_z are the input light position.

L_r,L_g,L_b, the light color vector, is a function of position in the spot light case only:

L_r = Light_r*pow((-L.S),specularExponent)
L_g = Light_g*pow((-L.S),specularExponent)
L_b = Light_b*pow((-L.S),specularExponent)

where S is the unit vector pointing from the light to the point (pointsAtX, pointsAtY, pointsAtZ) in the x-y plane:

S_x = pointsAtX - Light_x
S_y = pointsAtY - Light_y
S_z = pointsAtZ - Light_z

S = (S_x, S_y, S_z) / Norm(S_x, S_y, S_z)

If L.S is positive, no light is present. (L_r = L_g = L_b = 0). If ‘limitingConeAngle’ is specified, -L.S < cos(limitingConeAngle) also indicates that no light is present.

Attribute definitions:

surfaceScale = "<number>"

height of surface when A_in = 1.
If the attribute is not specified, then the effect is as if a value of 1 were specified.
Animatable: yes.

diffuseConstant = "<number>"

kd in Phong lighting model. In SVG, this can be any non-negative number.
If the attribute is not specified, then the effect is as if a value of 1 were specified.
Animatable: yes.

kernelUnitLength = "<number-optional-number>"

The first number is the <dx> value. The second number is the <dy> value. If the <dy> value is not specified, it defaults to the same value as <dx>. Indicates the intended distance in current filter units (i.e., units as determined by the value of attribute ‘primitiveUnits’) for dx and dy, respectively, in the surface normal calculation formulas. By specifying value(s) for kernelUnitLength, the kernel becomes defined in a scalable, abstract coordinate system. If kernelUnitLength is not specified, the dx and dy values should represent very small deltas relative to a given (x,y) position, which might be implemented in some cases as one pixel in the intermediate image offscreen bitmap, which is a pixel-based coordinate system, and thus potentially not scalable. For some level of consistency across display media and user agents, it is necessary that a value be provided for at least one of ‘filterRes’ and kernelUnitLength. Discussion of intermediate images are in the Introduction and in the description of attribute ‘filterRes’.
If a negative or zero value is specified the default value will be used instead.
Animatable: yes.

The light source is defined by one of the child elements <feDistantLight>, <fePointLight> or <feSpotLight>. The light color is specified by property ‘lighting-color’.

8.11. Filter primitive <feDisplacementMap>

Name:	feDisplacementMap
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘in2’ ‘scale’ ‘xChannelSelector’ ‘yChannelSelector’
DOM Interfaces:	SVGFEDisplacementMapElement

This filter primitive uses the pixels values from the image from ‘in2’ to spatially displace the image from ‘in’. This is the transformation to be performed:

 P'(x,y) ← P( x + scale * (XC(x,y) - .5), y + scale * (YC(x,y) - .5))
  

where P(x,y) is the input image, ‘in’, and P'(x,y) is the destination. XC(x,y) and YC(x,y) are the component values of the channel designated by the ‘xChannelSelector’ and ‘yChannelSelector’. For example, to use the R component of ‘in2’ to control displacement in x and the G component of Image2 to control displacement in y, set ‘xChannelSelector’ to "R" and ‘yChannelSelector’ to "G".

The displacement map, ‘in2’, defines the inverse of the mapping performed.

The input image in is to remain premultiplied for this filter primitive. The calculations using the pixel values from ‘in2’ are performed using non-premultiplied color values. If the image from ‘in2’ consists of premultiplied color values, those values are automatically converted into non-premultiplied color values before performing this operation.

This filter can have arbitrary non-localized effect on the input which might require substantial buffering in the processing pipeline. However with this formulation, any intermediate buffering needs can be determined by ‘scale’ which represents the maximum range of displacement in either x or y.

When applying this filter, the source pixel location will often lie between several source pixels. In this case it is recommended that high quality viewers apply an interpolent on the surrounding pixels, for example bilinear or bicubic, rather than simply selecting the nearest source pixel. Depending on the speed of the available interpolents, this choice may be affected by the ‘image-rendering’ property setting.

The ‘color-interpolation-filters’ property only applies to the ‘in2’ source image and does not apply to the ‘in’ source image. The ‘in’ source image must remain in its current color space.

Attribute definitions:

scale = "<number>"

Displacement scale factor. The amount is expressed in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
When the value of this attribute is 0, this operation has no effect on the source image.

The lacuna value for ‘scale’ is 0.

Animatable: yes.

xChannelSelector = "R | G | B | A"

Indicates which channel from ‘in2’ to use to displace the pixels in ‘in’ along the x-axis. The lacuna value for ‘xChannelSelector’ is A.
Animatable: yes.

yChannelSelector = "R | G | B | A"

Indicates which channel from ‘in2’ to use to displace the pixels in ‘in’ along the y-axis. The lacuna value for ‘yChannelSelector’ is A.
Animatable: yes.

in2 = "(see ‘in’ attribute)"

The second input image, which is used to displace the pixels in the image from attribute ‘in’. This attribute can take on the same values as the ‘in’ attribute.
Animatable: yes.

8.12. Filter primitive <feDropShadow>

Name:	feDropShadow
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘stdDeviation’ ‘dx’ ‘dy’
DOM Interfaces:	SVGFEDropShadowElement

This filter creates a drop shadow of the input image. It is a shorthand filter, and is defined in terms of combinations of other filter primitives. The expectation is that it can be optimized more easily by implementations.

The result of a <feDropShadow> filter primitive is equivalent to the following:

  <feGaussianBlur in="alpha-channel-of-feDropShadow-in" stdDeviation="stdDeviation-of-feDropShadow"/> 
  <feOffset dx="dx-of-feDropShadow" dy="dy-of-feDropShadow" result="offsetblur"/> 
  <feFlood flood-color="flood-color-of-feDropShadow" flood-opacity="flood-opacity-of-feDropShadow"/> 
  <feComposite in2="offsetblur" operator="in"/> 
  <feMerge> 
    <feMergeNode/>
    <feMergeNode in="in-of-feDropShadow"/> 
  </feMerge>

The above divided into steps:

1. Take the alpha channel of the input to the <feDropShadow> filter primitive and the ‘stdDeviation’ on the <feDropShadow> and do processing as if the following <feGaussianBlur> was applied:

    <feGaussianBlur in="alpha-channel-of-feDropShadow-in" stdDeviation="stdDeviation-of-feDropShadow"/>

   
   
2. Offset the result of step 1 by ‘dx’ and ‘dy’ as specified on the <feDropShadow> element, equivalent to applying an <feOffset> with these parameters:

    <feOffset dx="dx-of-feDropShadow" dy="dy-of-feDropShadow" result="offsetblur"/>

   
   
3. Do processing as if an <feFlood> element with ‘flood-color’ and ‘flood-opacity’ as specified on the <feDropShadow> was applied:

    <feFlood flood-color="flood-color-of-feDropShadow" flood-opacity="flood-opacity-of-feDropShadow"/>

   
   
4. Composite the result of the <feFlood> in step 3 with the result of the <feOffset> in step 2 as if an <feComposite> filter primitive with operator=‘in’ was applied:

    <feComposite in2="offsetblur" operator="in"/>

   
   
5. Finally merge the result of the previous step, doing processing as if the following <feMerge> was performed:

    <feMerge>
         <feMergeNode/>
         <feMergeNode in="in-of-feDropShadow"/>
     </feMerge>

Note that while the definition of the <feDropShadow> filter primitive says that it can be expanded into an equivalent tree it is not required that it is implemented like that. The expectation is that user agents can optimize the handling by not having to do all the steps separately.

Beyond the DOM interface SVGFEDropShadowElement there is no way of accessing the internals of the <feDropShadow> filter primitive, meaning if the filter primitive is implemented as an equivalent tree then that tree must not be exposed to the DOM.

Attribute definitions:

dx = "<number>"

The x offset of the drop shadow.

The lacuna value for ‘dx’ is 2.

This attribute is then forwarded to the ‘dx’ attribute of the internal <feOffset> element.

Animatable: yes.

dy = "<number>"

The y offset of the drop shadow.

The lacuna value for ‘dy’ is 2.

This attribute is then forwarded to the ‘dy’ attribute of the internal <feOffset> element.

Animatable: yes.

stdDeviation = "<number-optional-number>"

The standard deviation for the blur operation in the drop shadow.

The lacuna value for ‘stdDeviation’ is 2.

This attribute is then forwarded to the ‘stdDeviation’ attribute of the internal <feGaussianBlur> element.

Animatable: yes.

8.13. Filter primitive <feFlood>

Name:	feFlood
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set> <animateColor>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’
DOM Interfaces:	SVGFEFloodElement

This filter primitive creates a rectangle filled with the color and opacity values from properties ‘flood-color’ and ‘flood-opacity’. The rectangle is as large as the filter primitive subregion established by the <feFlood> element.

 

8.13.1. The ‘flood-color’ property

The ‘flood-color’ property indicates what color to use to flood the current filter primitive subregion. The keyword ‘currentColor’ and ICC colors can be specified in the same manner as within a <paint> specification for the ‘fill’ and ‘stroke’ properties.

Name:	flood-color
Value:	currentColor | <color> <icccolor>?
Initial:	black
Applies to:	<feFlood> and <feDropShadow> elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

8.13.2. The ‘flood-opacity’ property

The ‘flood-opacity’ property defines the opacity value to use across the entire filter primitive subregion.

Name:	flood-opacity
Value:	<number> | <percentage>
Initial:	1
Applies to:	<feFlood> and <feDropShadow> elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

8.14. Filter primitive <feGaussianBlur>

Name:	feGaussianBlur
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘stdDeviation’
DOM Interfaces:	SVGFEGaussianBlurElement

This filter primitive performs a Gaussian blur on the input image.

The Gaussian blur kernel is an approximation of the normalized convolution:

G(x,y) = H(x)I(y)

where

H(x) = exp(-x²/ (2s²)) / sqrt(2* pi*s²)

and

I(x) = exp(-y²/ (2t²)) / sqrt(2* pi*t²)

with ‘s’ being the standard deviation in the x direction and ‘t’ being the standard deviation in the y direction, as specified by ‘stdDeviation’.

The value of ‘stdDeviation’ can be either one or two numbers. If two numbers are provided, the first number represents a standard deviation value along the x-axis of the current coordinate system and the second value represents a standard deviation in Y. If one number is provided, then that value is used for both X and Y.

Even if only one value is provided for ‘stdDeviation’, this can be implemented as a separable convolution.

For larger values of ‘s’ (s >= 2.0), an approximation can be used: Three successive box-blurs build a piece-wise quadratic convolution kernel, which approximates the Gaussian kernel to within roughly 3%.

let d = floor(s * 3*sqrt(2*pi)/4 + 0.5)

... if d is odd, use three box-blurs of size ‘d’, centered on the output pixel.

... if d is even, two box-blurs of size ‘d’ (the first one centered on the pixel boundary between the output pixel and the one to the left, the second one centered on the pixel boundary between the output pixel and the one to the right) and one box blur of size ‘d+1’ centered on the output pixel.

The approximation formula also applies correspondingly to ‘t’.

Frequently this operation will take place on alpha-only images, such as that produced by the built-in input, SourceAlpha. The implementation may notice this and optimize the single channel case. If the input has infinite extent and is constant (e.g FillPaint where the fill is a solid color), this operation has no effect. If the input has infinite extent and the filter resultwhere the fill is a solid color) is the input to an <feTile>, the filter is evaluated with periodic boundary conditions.

By default, the subregion interacts as input and output clipping and this sentence would be irrelevant. However, this changes if the WG decides to allow a choice between input and output clipping.

What about other inputs with infinite extents? What is the ‘periodic boundary condition’?

Attribute definitions:

stdDeviation = "<number-optional-number>"

The standard deviation for the blur operation. If two <number> s are provided, the first number represents a standard deviation value along the x-axis of the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element. The second value represents a standard deviation in Y. If one number is provided, then that value is used for both X and Y.
A value of zero disables the effect of the given filter primitive (i.e., the result is the filter input image).
If ‘stdDeviation’ is 0 in only one of X or Y, then the effect is that the blur is only applied in the direction that has a non-zero value.
The lacuna value for ‘stdDeviation’ is 0.
Animatable: yes.

The example at the start of this chapter makes use of the <feGaussianBlur> filter primitive to create a drop shadow effect.

8.15. Filter primitive <feImage>

Name:	feImage
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set> <animateTransform>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ xlink attributes — ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’ ‘class’ ‘style’ ‘externalResourcesRequired’ ‘preserveAspectRatio’ ‘xlink:href’
DOM Interfaces:	SVGFEImageElement

This filter primitive refers to a graphic external to this filter element, which is loaded or rendered into an RGBA raster and becomes the result of the filter primitive.

This filter primitive can refer to an external image or can be a reference to another piece of SVG. It produces an image similar to the built-in image source SourceGraphic except that the graphic comes from an external source.

If the xlink:href references a stand-alone image resource such as a JPEG, PNG or SVG file, then the image resource is rendered according to the behavior of the <image> element; otherwise, the referenced resource is rendered according to the behavior of the <use> element. In either case, the current user coordinate system depends on the value of attribute ‘primitiveUnits’ on the <filter> element. The processing of the preserveAspectRatio attribute on the <feImage> element is identical to that of the <image> element.

When the referenced image must be resampled to match the device coordinate system, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the ‘image-rendering’ property setting.

Attribute definitions:

xlink:href = "<IRI>"

An IRI reference to an image resource or to an element.
Animatable: yes.

preserveAspectRatio = "[defer] <align> [<meetOrSlice>]"

See ‘preserveAspectRatio’.

The lacuna value for ‘preserveAspectRatio’ is xMidYMid meet.

Animatable: yes.

The following example illustrates how images are placed relative to an object. From left to right:

• The default placement of an image. Note that the image is centered in the filter region and has the maximum size that will fit in the region consistent with preserving the aspect ratio.
• The image stretched to fit the bounding box of an object.
• The image placed using user coordinates. Note that the image is first centered in a box the size of the filter region and has the maximum size that will fit in the box consistent with preserving the aspect ratio. This box is then shifted by the given ‘x’ and ‘y’ values relative to the viewport the object is in.

<svg width="600" height="250" viewBox="0 0 600 250"
     xmlns="https://www.w3.org/2000/svg"
     xmlns:xlink="https://www.w3.org/1999/xlink">
  <title>Example feImage - Examples of feImage use</title>
  <desc>Three examples of using feImage, the first showing the
        default rendering, the second showing the image fit
        to a box and the third showing the image
        shifted and clipped.</desc>
  <defs>
    <filter id="Default">
      <feImage xlink:href="smiley.png" />
    </filter>
    <filter id="Fitted" primitiveUnits="objectBoundingBox">
      <feImage xlink:href="smiley.png"
         x="0" y="0" width="100%" height="100%"
         preserveAspectRatio="none"/>
    </filter>
    <filter id="Shifted">
      <feImage xlink:href="smiley.png"
         x="500" y="5"/>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="598" height="248"/>
  <g>
    <rect x="50"  y="25" width="100" height="200" filter="url(#Default)"/>
    <rect x="50"  y="25" width="100" height="200" fill="none" stroke="green"/>
    <rect x="250" y="25" width="100" height="200" filter="url(#Fitted)"/>
    <rect x="250" y="25" width="100" height="200" fill="none" stroke="green"/>
    <rect x="450" y="25" width="100" height="200" filter="url(#Shifted)"/>
    <rect x="450" y="25" width="100" height="200" fill="none" stroke="green"/>
  </g>
</svg>

Example of feImage

View this example as SVG (SVG-enabled browsers only)

8.16. Filter primitive <feMerge>

Name:	feMerge
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <feMergeNode>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’
DOM Interfaces:	SVGFEMergeElement

This filter primitive composites input image layers on top of each other using the over operator with Input1 (corresponding to the first <feMergeNode> child element) on the bottom and the last specified input, InputN (corresponding to the last <feMergeNode> child element), on top.

Many effects produce a number of intermediate layers in order to create the final output image. This filter allows us to collapse those into a single image. Although this could be done by using n-1 Composite-filters, it is more convenient to have this common operation available in this form, and offers the implementation some additional flexibility.

Each ‘feMerge’ element can have any number of ‘feMergeNode’ subelements, each of which has an in attribute.

Name:	feMergeNode
Categories:	None.
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘in’
DOM Interfaces:	SVGFEMergeNodeElement

The canonical implementation of feMerge is to render the entire effect into one RGBA layer, and then render the resulting layer on the output device. In certain cases (in particular if the output device itself is a continuous tone device), and since merging is associative, it might be a sufficient approximation to evaluate the effect one layer at a time and render each layer individually onto the output device bottom to top.

If the topmost image input is SourceGraphic and this <feMerge> is the last filter primitive in the filter, the implementation is encouraged to render the layers up to that point, and then render the SourceGraphic directly from its vector description on top.

The example at the start of this chapter makes use of the <feMerge> filter primitive to composite two intermediate filter results together.

8.17. Filter primitive <feMorphology>

Name:	feMorphology
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘operator’ ‘radius’
DOM Interfaces:	SVGFEMorphologyElement

This filter primitive performs "fattening" or "thinning" of artwork. It is particularly useful for fattening or thinning an alpha channel.

The dilation (or erosion) kernel is a rectangle with a width of 2*x-radius and a height of 2*y-radius. In dilation, the output pixel is the individual component-wise maximum of the corresponding R,G,B,A values in the input image's kernel rectangle. In erosion, the output pixel is the individual component-wise minimum of the corresponding R,G,B,A values in the input image's kernel rectangle.

Frequently this operation will take place on alpha-only images, such as that produced by the built-in input, SourceAlpha. In that case, the implementation might want to optimize the single channel case.

If the input has infinite extent and is constant (e.g FillPaint where the fill is a solid color), this operation has no effect. If the input has infinite extent and the filter result is the input to an <feTile>, the filter is evaluated with periodic boundary conditions.

By default, the subregion interacts as input and output clipping and this sentence would be irrelevant. However, this changes if the WG decides to allow a choice between input and output clipping.

What about other inputs with infinite extents? What is the ‘periodic boundary condition’?

Because <feMorphology> operates on premultipied color values, it will always result in color values less than or equal to the alpha channel.

Attribute definitions:

operator = "erode | dilate"

A keyword indicating whether to erode (i.e., thin) or dilate (fatten) the source graphic. The lacuna value for ‘operator’ is erode.
Animatable: yes.

radius = "<number-optional-number>"

The radius (or radii) for the operation. If two <number> s are provided, the first number represents a x-radius and the second value represents a y-radius. If one number is provided, then that value is used for both X and Y. The values are in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
A negative or zero value disables the effect of the given filter primitive (i.e., the result is a transparent black image).
If the attribute is not specified, then the effect is as if a value of 0 were specified.
Animatable: yes.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="5cm" height="7cm" viewBox="0 0 700 500"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example feMorphology - Examples of erode and dilate</title>
  <desc>Five text strings drawn as outlines.
        The first is unfiltered. The second and third use 'erode'.
        The fourth and fifth use 'dilate'.</desc>
  <defs>
    <filter id="Erode3">
      <feMorphology operator="erode" in="SourceGraphic" radius="3" />
    </filter>
    <filter id="Erode6">
      <feMorphology operator="erode" in="SourceGraphic" radius="6" />
    </filter>
    <filter id="Dilate3">
      <feMorphology operator="dilate" in="SourceGraphic" radius="3" />
    </filter>
    <filter id="Dilate6">
      <feMorphology operator="dilate" in="SourceGraphic" radius="6" />
    </filter>
  </defs>
  <rect fill="none" stroke="blue" stroke-width="2"  
        x="1" y="1" width="698" height="498"/>
  <g enable-background="new" >
    <g font-family="Verdana" font-size="75" 
              fill="none" stroke="black" stroke-width="6" >
      <text x="50" y="90">Unfiltered</text>
      <text x="50" y="180" filter="url(#Erode3)" >Erode radius 3</text>
      <text x="50" y="270" filter="url(#Erode6)" >Erode radius 6</text>
      <text x="50" y="360" filter="url(#Dilate3)" >Dilate radius 3</text>
      <text x="50" y="450" filter="url(#Dilate6)" >Dilate radius 6</text>
    </g>
  </g>
</svg>

Example of feMorphology

View this example as SVG (SVG-enabled browsers only)

8.18. Filter primitive <feOffset>

Name:	feOffset
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘dx’ ‘dy’
DOM Interfaces:	SVGFEOffsetElement

This filter primitive offsets the input image relative to its current position in the image space by the specified vector.

This is important for effects like drop shadows.

When applying this filter, the destination location may be offset by a fraction of a pixel in device space. In this case a high quality viewer should make use of appropriate interpolation techniques, for example bilinear or bicubic. This is especially recommended for dynamic viewers where this interpolation provides visually smoother movement of images. For static viewers this is less of a concern. Close attention should be made to the ‘image-rendering’ property setting to determine the authors intent.

Attribute definitions:

dx = "<number>"

The amount to offset the input graphic along the x-axis. The offset amount is expressed in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
If the attribute is not specified, then the effect is as if a value of 0 were specified.
Animatable: yes.

dy = "<number>"

The amount to offset the input graphic along the y-axis. The offset amount is expressed in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
If the attribute is not specified, then the effect is as if a value of 0 were specified.
Animatable: yes.

The example at the start of this chapter makes use of the <feOffset> filter primitive to offset the drop shadow from the original source graphic.

8.19. Filter primitive <feSpecularLighting>

Name:	feSpecularLighting
Categories:	Filter primitive element
Content model:	Any number of descriptive elements and exactly one light source element, in any order.
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’ ‘surfaceScale’ ‘specularConstant’ ‘specularExponent’ ‘kernelUnitLength’
DOM Interfaces:	SVGFESpecularLightingElement

This filter primitive lights a source graphic using the alpha channel as a bump map. The resulting image is an RGBA image based on the light color. The lighting calculation follows the standard specular component of the Phong lighting model. The resulting image depends on the light color, light position and surface geometry of the input bump map. The result of the lighting calculation is added. The filter primitive assumes that the viewer is at infinity in the z direction (i.e., the unit vector in the eye direction is (0,0,1) everywhere).

This filter primitive produces an image which contains the specular reflection part of the lighting calculation. Such a map is intended to be combined with a texture using the add term of the arithmetic <feComposite> method. Multiple light sources can be simulated by adding several of these light maps before applying it to the texture image.

The resulting RGBA image is computed as follows:

S_r = k_s * pow(N.H, specularExponent) * L_r
S_g = k_s * pow(N.H, specularExponent) * L_g
S_b = k_s * pow(N.H, specularExponent) * L_b
S_a = max(S_r, S_g, S_b)

where

k_s = specular lighting constant
N = surface normal unit vector, a function of x and y
H = "halfway" unit vector between eye unit vector and light unit vector

L_r,L_g,L_b = RGB components of light

See <feDiffuseLighting> for definition of N and (L_r, L_g, L_b).

The definition of H reflects our assumption of the constant eye vector E = (0,0,1):

H = (L + E) / Norm(L+E)

where L is the light unit vector.

Unlike the <feDiffuseLighting>, the <feSpecularLighting> filter produces a non-opaque image. This is due to the fact that the specular result (S_r,S_g,S_b,S_a) is meant to be added to the textured image. The alpha channel of the result is the max of the color components, so that where the specular light is zero, no additional coverage is added to the image and a fully white highlight will add opacity.

The <feDiffuseLighting> and <feSpecularLighting> filters will often be applied together. An implementation may detect this and calculate both maps in one pass, instead of two.

Attribute definitions:

surfaceScale = "<number>"

height of surface when A_in = 1.
If the attribute is not specified, then the effect is as if a value of 1 were specified.
Animatable: yes.

specularConstant = "<number>"

ks in Phong lighting model. In SVG, this can be any non-negative number.
If the attribute is not specified, then the effect is as if a value of 1 were specified.
Animatable: yes.

specularExponent = "<number>"

Exponent for specular term, larger is more "shiny". Range 1.0 to 128.0.
If the attribute is not specified, then the effect is as if a value of 1 were specified.
Animatable: yes.

kernelUnitLength = "<number-optional-number>"

The first number is the <dx> value. The second number is the <dy> value. If the <dy> value is not specified, it defaults to the same value as <dx>. Indicates the intended distance in current filter units (i.e., units as determined by the value of attribute ‘primitiveUnits’) for dx and dy, respectively, in the surface normal calculation formulas. By specifying value(s) for kernelUnitLength, the kernel becomes defined in a scalable, abstract coordinate system. If kernelUnitLength is not specified, the dx and dy values should represent very small deltas relative to a given (x,y) position, which might be implemented in some cases as one pixel in the intermediate image offscreen bitmap, which is a pixel-based coordinate system, and thus potentially not scalable. For some level of consistency across display media and user agents, it is necessary that a value be provided for at least one of filterRes and kernelUnitLength. Discussion of intermediate images are in the Introduction and in the description of attribute ‘filterRes’.
If a negative or zero value is specified the default value will be used instead.
Animatable: yes.

The light source is defined by one of the child elements <feDistantLight>, <fePointLight> or <feDistantLight>. The light color is specified by property ‘lighting-color’.

The example at the start of this chapter makes use of the <feSpecularLighting> filter primitive to achieve a highly reflective, 3D glowing effect.

8.20. Filter primitive <feTile>

Name:	feTile
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘in’
DOM Interfaces:	SVGFETileElement

This filter primitive fills a target rectangle with a repeated, tiled pattern of an input image. The target rectangle is as large as the filter primitive subregion established by the <feTile> element.

Typically, the input image has been defined with its own filter primitive subregion in order to define a reference tile. <feTile> replicates the reference tile in both X and Y to completely fill the target rectangle. The top/left corner of each given tile is at location (x+i*width,y+j*height), where (x,y) represents the top/left of the input image's filter primitive subregion, width and height represent the width and height of the input image's filter primitive subregion, and i and j can be any integer value. In most cases, the input image will have a smaller filter primitive subregion than the <feTile> in order to achieve a repeated pattern effect.

Implementers must take appropriate measures in constructing the tiled image to avoid artifacts between tiles, particularly in situations where the user to device transform includes shear and/or rotation. Unless care is taken, interpolation can lead to edge pixels in the tile having opacity values lower or higher than expected due to the interaction of painting adjacent tiles which each have partial overlap with particular pixels.

 

8.21. Filter primitive <feTurbulence>

Name:	feTurbulence
Categories:	Filter primitive element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ presentation attributes — ‘alignment-baseline’, ‘baseline-shift’, ‘clip’, ‘clip-path’, ‘clip-rule’, ‘color’, ‘color-interpolation’, ‘color-interpolation-filters’, ‘color-profile’, ‘color-rendering’, ‘cursor’, ‘direction’, ‘display’, ‘dominant-baseline’, ‘enable-background’, ‘fill’, ‘fill-opacity’, ‘fill-rule’, ‘filter’, ‘flood-color’, ‘flood-opacity’, ‘font’, ‘font-family’, ‘font-size’, ‘font-size-adjust’, ‘font-stretch’, ‘font-style’, ‘font-variant’, ‘font-weight’, ‘glyph-orientation-horizontal’, ‘glyph-orientation-vertical’, ‘image-rendering’, ‘kerning’, ‘letter-spacing’, ‘lighting-color’, ‘marker’, ‘marker-end’, ‘marker-mid’, ‘marker-start’, ‘mask’, ‘mix-blend-mode’, ‘opacity’, ‘overflow’, ‘pointer-events’, ‘shape-rendering’, ‘stop-color’, ‘stop-opacity’, ‘stroke’, ‘stroke-dasharray’, ‘stroke-dashoffset’, ‘stroke-linecap’, ‘stroke-linejoin’, ‘stroke-miterlimit’, ‘stroke-opacity’, ‘stroke-width’, ‘text-anchor’, ‘text-decoration’, ‘text-rendering’, ‘unicode-bidi’, ‘visibility’, ‘word-spacing’, ‘writing-mode’ filter primitive attributes — ‘x’, ‘y’, ‘width’, ‘height’, ‘result’ ‘class’ ‘style’ ‘baseFrequency’ ‘numOctaves’ ‘seed’ ‘stitchTiles’ ‘type’
DOM Interfaces:	SVGFETurbulenceElement

This filter primitive creates an image using the Perlin turbulence function. It allows the synthesis of artificial textures like clouds or marble. For a detailed description the of the Perlin turbulence function, see "Texturing and Modeling", Ebert et al, AP Professional, 1994. The resulting image will fill the entire filter primitive subregion for this filter primitive.

It is possible to create bandwidth-limited noise by synthesizing only one octave.

The C code below shows the exact algorithm used for this filter effect. The filter primitive subregion is to be passed as the arguments fTileX, fTileY, fTileWidth and fTileHeight.

For fractalSum, you get a turbFunctionResult that is aimed at a range of -1 to 1 (the actual result might exceed this range in some cases). To convert to a color value, use the formula colorValue = ((turbFunctionResult * 255) + 255) / 2, then clamp to the range 0 to 255.

For turbulence, you get a turbFunctionResult that is aimed at a range of 0 to 1 (the actual result might exceed this range in some cases). To convert to a color value, use the formula colorValue = (turbFunctionResult * 255), then clamp to the range 0 to 255.

The following order is used for applying the pseudo random numbers. An initial seed value is computed based on the ‘seed’ attribute. Then the implementation computes the lattice points for R, then continues getting additional pseudo random numbers relative to the last generated pseudo random number and computes the lattice points for G, and so on for B and A.

The generated color and alpha values are in the color space determined by the ‘color-interpolation-filters’ property:

/* Produces results in the range [1, 2**31 - 2].
Algorithm is: r = (a * r) mod m
where a = 16807 and m = 2**31 - 1 = 2147483647
See [Park & Miller], CACM vol. 31 no. 10 p. 1195, Oct. 1988
To test: the algorithm should produce the result 1043618065
as the 10,000th generated number if the original seed is 1.
*/
#define RAND_m 2147483647 /* 2**31 - 1 */
#define RAND_a 16807 /* 7**5; primitive root of m */
#define RAND_q 127773 /* m / a */
#define RAND_r 2836 /* m % a */
long setup_seed(long lSeed)
{
  if (lSeed <= 0) lSeed = -(lSeed % (RAND_m - 1)) + 1;
  if (lSeed > RAND_m - 1) lSeed = RAND_m - 1;
  return lSeed;
}
long random(long lSeed)
{
  long result;
  result = RAND_a * (lSeed % RAND_q) - RAND_r * (lSeed / RAND_q);
  if (result <= 0) result += RAND_m;
  return result;
}
#define BSize 0x100
#define BM 0xff
#define PerlinN 0x1000
#define NP 12 /* 2^PerlinN */
#define NM 0xfff
static uLatticeSelector[BSize + BSize + 2];
static double fGradient[4][BSize + BSize + 2][2];
struct StitchInfo
{
  int nWidth; // How much to subtract to wrap for stitching.
  int nHeight;
  int nWrapX; // Minimum value to wrap.
  int nWrapY;
};
static void init(long lSeed)
{
  double s;
  int i, j, k;
  lSeed = setup_seed(lSeed);
  for(k = 0; k < 4; k++)
  {
    for(i = 0; i < BSize; i++)
    {
      uLatticeSelector[i] = i;
      for (j = 0; j < 2; j++)
        fGradient[k][i][j] = (double)(((lSeed = random(lSeed)) % (BSize + BSize)) - BSize) / BSize;
      s = double(sqrt(fGradient[k][i][0] * fGradient[k][i][0] + fGradient[k][i][1] * fGradient[k][i][1]));
      fGradient[k][i][0] /= s;
      fGradient[k][i][1] /= s;
    }
  }
  while(--i)
  {
    k = uLatticeSelector[i];
    uLatticeSelector[i] = uLatticeSelector[j = (lSeed = random(lSeed)) % BSize];
    uLatticeSelector[j] = k;
  }
  for(i = 0; i < BSize + 2; i++)
  {
    uLatticeSelector[BSize + i] = uLatticeSelector[i];
    for(k = 0; k < 4; k++)
      for(j = 0; j < 2; j++)
        fGradient[k][BSize + i][j] = fGradient[k][i][j];
  }
}
#define s_curve(t) ( t * t * (3. - 2. * t) )
#define lerp(t, a, b) ( a + t * (b - a) )
double noise2(int nColorChannel, double vec[2], StitchInfo *pStitchInfo)
{
  int bx0, bx1, by0, by1, b00, b10, b01, b11;
  double rx0, rx1, ry0, ry1, *q, sx, sy, a, b, t, u, v;
  register i, j;
  t = vec[0] + PerlinN;
  bx0 = (int)t;
  bx1 = bx0+1;
  rx0 = t - (int)t;
  rx1 = rx0 - 1.0f;
  t = vec[1] + PerlinN;
  by0 = (int)t;
  by1 = by0+1;
  ry0 = t - (int)t;
  ry1 = ry0 - 1.0f;
  // If stitching, adjust lattice points accordingly.
  if(pStitchInfo != NULL)
  {
    if(bx0 >= pStitchInfo->nWrapX)
      bx0 -= pStitchInfo->nWidth;
    if(bx1 >= pStitchInfo->nWrapX)
      bx1 -= pStitchInfo->nWidth;
    if(by0 >= pStitchInfo->nWrapY)
      by0 -= pStitchInfo->nHeight;
    if(by1 >= pStitchInfo->nWrapY)
      by1 -= pStitchInfo->nHeight;
  }
  bx0 &= BM;
  bx1 &= BM;
  by0 &= BM;
  by1 &= BM;
  i = uLatticeSelector[bx0];
  j = uLatticeSelector[bx1];
  b00 = uLatticeSelector[i + by0];
  b10 = uLatticeSelector[j + by0];
  b01 = uLatticeSelector[i + by1];
  b11 = uLatticeSelector[j + by1];
  sx = double(s_curve(rx0));
  sy = double(s_curve(ry0));
  q = fGradient[nColorChannel][b00]; u = rx0 * q[0] + ry0 * q[1];
  q = fGradient[nColorChannel][b10]; v = rx1 * q[0] + ry0 * q[1];
  a = lerp(sx, u, v);
  q = fGradient[nColorChannel][b01]; u = rx0 * q[0] + ry1 * q[1];
  q = fGradient[nColorChannel][b11]; v = rx1 * q[0] + ry1 * q[1];
  b = lerp(sx, u, v);
  return lerp(sy, a, b);
}
double turbulence(int nColorChannel, double *point, double fBaseFreqX, double fBaseFreqY,
          int nNumOctaves, bool bFractalSum, bool bDoStitching,
          double fTileX, double fTileY, double fTileWidth, double fTileHeight)
{
  StitchInfo stitch;
  StitchInfo *pStitchInfo = NULL; // Not stitching when NULL.
  // Adjust the base frequencies if necessary for stitching.
  if(bDoStitching)
  {
    // When stitching tiled turbulence, the frequencies must be adjusted
    // so that the tile borders will be continuous.
    if(fBaseFreqX != 0.0)
    {
      double fLoFreq = double(floor(fTileWidth * fBaseFreqX)) / fTileWidth;
      double fHiFreq = double(ceil(fTileWidth * fBaseFreqX)) / fTileWidth;
      if(fBaseFreqX / fLoFreq < fHiFreq / fBaseFreqX)
        fBaseFreqX = fLoFreq;
      else
        fBaseFreqX = fHiFreq;
    }
    if(fBaseFreqY != 0.0)
    {
      double fLoFreq = double(floor(fTileHeight * fBaseFreqY)) / fTileHeight;
      double fHiFreq = double(ceil(fTileHeight * fBaseFreqY)) / fTileHeight;
      if(fBaseFreqY / fLoFreq < fHiFreq / fBaseFreqY)
        fBaseFreqY = fLoFreq;
      else
        fBaseFreqY = fHiFreq;
    }
    // Set up initial stitch values.
    pStitchInfo = &stitch;
    stitch.nWidth = int(fTileWidth * fBaseFreqX + 0.5f);
    stitch.nWrapX = fTileX * fBaseFreqX + PerlinN + stitch.nWidth;
    stitch.nHeight = int(fTileHeight * fBaseFreqY + 0.5f);
    stitch.nWrapY = fTileY * fBaseFreqY + PerlinN + stitch.nHeight;
  }
  double fSum = 0.0f;
  double vec[2];
  vec[0] = point[0] * fBaseFreqX;
  vec[1] = point[1] * fBaseFreqY;
  double ratio = 1;
  for(int nOctave = 0; nOctave < nNumOctaves; nOctave++)
  {
    if(bFractalSum)
      fSum += double(noise2(nColorChannel, vec, pStitchInfo) / ratio);
    else
      fSum += double(fabs(noise2(nColorChannel, vec, pStitchInfo)) / ratio);
    vec[0] *= 2;
    vec[1] *= 2;
    ratio *= 2;
    if(pStitchInfo != NULL)
    {
      // Update stitch values. Subtracting PerlinN before the multiplication and
      // adding it afterward simplifies to subtracting it once.
      stitch.nWidth *= 2;
      stitch.nWrapX = 2 * stitch.nWrapX - PerlinN;
      stitch.nHeight *= 2;
      stitch.nWrapY = 2 * stitch.nWrapY - PerlinN;
    }
  }
  return fSum;
}

Attribute definitions:

baseFrequency = "<number-optional-number>"

The base frequency (frequencies) parameter(s) for the noise function. If two <number>s are provided, the first number represents a base frequency in the X direction and the second value represents a base frequency in the Y direction. If one number is provided, then that value is used for both X and Y.

The lacuna value for ‘baseFrequency’ is 0.

Negative values are unsupported.

Animatable: yes.

numOctaves = "<integer>"

The numOctaves parameter for the noise function.

The lacuna value for ‘numOctaves’ is 1.

Negative values are unsupported.

Animatable: yes.

seed = "<number>"

The starting number for the pseudo random number generator.

The lacuna value for ‘seed’ is 0.

When the seed number is handed over to the algorithm above it must first be truncated, i.e. rounded to the closest integer value towards zero.

Animatable: yes.

stitchTiles = "stitch | noStitch"

If stitchTiles="noStitch", no attempt is made to achieve smooth transitions at the border of tiles which contain a turbulence function. Sometimes the result will show clear discontinuities at the tile borders.
If stitchTiles="stitch", then the user agent will automatically adjust baseFrequency-x and baseFrequency-y values such that the <feTurbulence> node's width and height (i.e., the width and height of the current subregion) contains an integral number of the Perlin tile width and height for the first octave. The baseFrequency will be adjusted up or down depending on which way has the smallest relative (not absolute) change as follows: Given the frequency, calculate lowFreq=floor(width*frequency)/width and hiFreq=ceil(width*frequency)/width. If frequency/lowFreq < hiFreq/frequency then use lowFreq, else use hiFreq. While generating turbulence values, generate lattice vectors as normal for Perlin Noise, except for those lattice points that lie on the right or bottom edges of the active area (the size of the resulting tile). In those cases, copy the lattice vector from the opposite edge of the active area.

The lacuna value for ‘stitchTiles’ is noStitch.

Animatable: yes.

type = "fractalNoise | turbulence"

Indicates whether the filter primitive should perform a noise or turbulence function.

The lacuna value for ‘type’ is turbulence.

Animatable: yes.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="450px" height="325px" viewBox="0 0 450 325"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example feTurbulence - Examples of feTurbulence operations</title>
  <desc>Six rectangular areas showing the effects of 
        various parameter settings for feTurbulence.</desc>
  <g  font-family="Verdana" text-anchor="middle" font-size="10" >
    <defs>
      <filter id="Turb1" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.05" numOctaves="2"/>
      </filter>
      <filter id="Turb2" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.1" numOctaves="2"/>
      </filter>
      <filter id="Turb3" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.05" numOctaves="8"/>
      </filter>
      <filter id="Turb4" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.1" numOctaves="4"/>
      </filter>
      <filter id="Turb5" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.4" numOctaves="4"/>
      </filter>
      <filter id="Turb6" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.1" numOctaves="1"/>
      </filter>
    </defs>
    <rect x="1" y="1" width="448" height="323"
          fill="none" stroke="blue" stroke-width="1"  />
    <rect x="25" y="25" width="100" height="75" filter="url(#Turb1)"  />
    <text x="75" y="117">type=turbulence</text>
    <text x="75" y="129">baseFrequency=0.05</text>
    <text x="75" y="141">numOctaves=2</text>
    <rect x="175" y="25" width="100" height="75" filter="url(#Turb2)"  />
    <text x="225" y="117">type=turbulence</text>
    <text x="225" y="129">baseFrequency=0.1</text>
    <text x="225" y="141">numOctaves=2</text>
    <rect x="325" y="25" width="100" height="75" filter="url(#Turb3)"  />
    <text x="375" y="117">type=turbulence</text>
    <text x="375" y="129">baseFrequency=0.05</text>
    <text x="375" y="141">numOctaves=8</text>
    <rect x="25" y="180" width="100" height="75" filter="url(#Turb4)"  />
    <text x="75" y="272">type=fractalNoise</text>
    <text x="75" y="284">baseFrequency=0.1</text>
    <text x="75" y="296">numOctaves=4</text>
    <rect x="175" y="180" width="100" height="75" filter="url(#Turb5)"  />
    <text x="225" y="272">type=fractalNoise</text>
    <text x="225" y="284">baseFrequency=0.4</text>
    <text x="225" y="296">numOctaves=4</text>
    <rect x="325" y="180" width="100" height="75" filter="url(#Turb6)"  />
    <text x="375" y="272">type=fractalNoise</text>
    <text x="375" y="284">baseFrequency=0.1</text>
    <text x="375" y="296">numOctaves=1</text>
  </g>
</svg>

Example of feTurbulence

View this example as SVG (SVG-enabled browsers only)

9. The ‘color-interpolation-filters’ property

The description of the ‘color-interpolation-filters’ property is as follows:

Name:	color-interpolation-filters
Value:	auto | sRGB | linearRGB
Initial:	linearRGB
Applies to:	filter primitives
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

‘auto’

Indicates that the user agent can choose either the ‘sRGB’ or ‘linearRGB’ spaces for filter effects color operations. This option indicates that the author doesn't require that color operations occur in a particular color space.

‘sRGB’

Indicates that filter effects color operations should occur in the sRGB color space.

‘linearRGB’

Indicates that filter effects color operations should occur in the linearized RGB color space.

The ‘color-interpolation-filters’ property specifies the color space for imaging operations performed via filter effects.

Note that ‘color-interpolation-filters’ has a different initial value than ‘color-interpolation’. ‘color-interpolation-filters’ has an initial value of ‘linearRGB’, where as ‘color-interpolation’ has an initial value of ‘sRGB’. Thus, in the default case, filter effects operations occur in the linearRGB color space, whereas all other color interpolations occur by default in the sRGB color space.

Note that the ‘color-interpolation-filters’ propert has no effect on Filter Functions, which operate in the sRGB color space.

10. Light source elements and properties

10.1. Introduction

The following sections define the elements that define a light source, <feDistantLight>, <fePointLight> and <feSpotLight>, and property ‘lighting-color’, which defines the color of the light.

10.2. Light source <feDistantLight>

Name:	feDistantLight
Categories:	Light source element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘azimuth’ ‘elevation’
DOM Interfaces:	SVGFEDistantLightElement

Attribute definitions:

azimuth = "<number>"

Direction angle for the light source on the XY plane (clockwise), in degrees from the x axis.
The lacuna value for ‘azimuth’ is 0.
Animatable: yes.

elevation = "<number>"

Direction angle for the light source from the XY plane towards the Z-axis, in degrees. Note that the positive Z-axis points towards the viewer.
The lacuna value for ‘elevation’ is 0.
Animatable: yes.

The following diagram illustrates the angles which ‘azimuth’ and ‘elevation’ represent in an XYZ coordinate system.

Angles which azimuth and elevation represent

Use other color then red and green

10.3. Light source <fePointLight>

Name:	fePointLight
Categories:	Light source element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘x’ ‘y’ ‘z’
DOM Interfaces:	SVGFEPointLightElement

Attribute definitions:

x = "<number>"

X location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
The lacuna value for ‘x’ is 0.
Animatable: yes.

y = "<number>"

Y location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
The lacuna value for ‘y’ is 0.
Animatable: yes.

z = "<number>"

Z location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element, assuming that, in the initial coordinate system , the positive Z-axis comes out towards the person viewing the content and assuming that one unit along the Z-axis equals one unit in X and Y.
The lacuna value for ‘z’ is 0.
Animatable: yes.

10.4. Light source <feSpotLight>

Name:	feSpotLight
Categories:	Light source element
Content model:	Any number of the following elements, in any order: <animate> <set>
Attributes:	core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’ ‘x’ ‘y’ ‘z’ ‘pointsAtX’ ‘pointsAtY’ ‘pointsAtZ’ ‘specularExponent’ ‘limitingConeAngle’
DOM Interfaces:	SVGFESpotLightElement

Attribute definitions:

x = "<number>"

X location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
The lacuna value for ‘x’ is 0.
Animatable: yes.

y = "<number>"

Y location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element.
The lacuna value for ‘y’ is 0.
Animatable: yes.

z = "<number>"

Z location for the light source in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element, assuming that, in the initial coordinate system , the positive Z-axis comes out towards the person viewing the content and assuming that one unit along the Z-axis equals one unit in X and Y.
The lacuna value for ‘z’ is 0.
Animatable: yes.

pointsAtX = "<number>"

X location in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element of the point at which the light source is pointing.
The lacuna value for ‘pointsAtX’ is 0.
Animatable: yes.

pointsAtY = "<number>"

Y location in the coordinate system established by attribute ‘primitiveUnits’ on the <filter> element of the point at which the light source is pointing.
The lacuna value for ‘pointsAtY’ is 0.
Animatable: yes.

pointsAtZ = "<number>"

Z location in the coordinate system established by the attribute ‘primitiveUnits’ on the <filter> element of the point at which the light source is pointing, assuming that, in the initial coordinate system, the positive Z-axis comes out towards the person viewing the content and assuming that one unit along the Z-axis equals one unit in X and Y.
The lacuna value for ‘pointsAtZ’ is 0.
Animatable: yes.

specularExponent = "<number>"

Exponent value controlling the focus for the light source.
The lacuna value for ‘specularExponent’ is 1.
Animatable: yes.

limitingConeAngle = "<number>"

A limiting cone which restricts the region where the light is projected. No light is projected outside the cone. limitingConeAngle represents the angle in degrees between the spot light axis (i.e. the axis between the light source and the point to which it is pointing at) and the spot light cone. User agents should apply a smoothing technique such as anti-aliasing at the boundary of the cone.
If no value is specified, then no limiting cone will be applied.
Animatable: yes.

10.5. The ‘lighting-color’ property

The ‘lighting-color’ property defines the color of the light source for filter primitives <feDiffuseLighting> and <feSpecularLighting>.

Name:	lighting-color
Value:	currentColor | <color> <icccolor>?
Initial:	white
Applies to:	<feDiffuseLighting> and <feSpecularLighting> elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

11. Custom Filter Function

The custom-filter function allows extending this specification with a customized filter effect. Customized filter effects are described by the @filter rule or feCustom element element and referenced internal or external resources. External resource must be described by a host language. Each @filter rule has a unique identifier that can be referenced by the custom-filter function.

11.1. The ‘@supports’ condition: ‘filter’

Value:

<custom-filter-type>

To verify if a UA supports a certain customized filter effect type, the support condition syntax [CSS3-CONDITIONAL] gets extended by adding the media feature ‘filter’.

<custom-filter-type> = webgl

This specification supports the custom filter type ‘webgl’ to indicate support for the shading language based on WebGL. Future versions may allow additional keywords.

@support filter(webgl) {
    ...
}

11.2. The @filter rule

The @filter rule allows specifying custom-filter definitions (like shaders) for the use of the ‘filter’ property. A @filter rule consists of the keyword "@filter", followed by an identifier giving a name for the custom-filter (which will be referenced using the ‘custom()’ filter function), followed by a set of custom-filter descriptors.

The general form of an @filter at-rule is:

@filter IDENT { <custom-filter-description> }

where <custom-filter-description> has the form:

descriptor: value;
descriptor: value;
[...]
descriptor: value;

Each @filter rule specifies a value for every custom-filter descriptor, either implicitly or explicitly. Those not given explicit values in the rule take the initial value listed with each descriptor in this specification. When a given descriptor occurs multiple times in a given @filter rule, only the last specified value is used, all prior values for that descriptor are ignored.

The following is the grammar for the custom-filter at-rule and extends the lexical scanner in the Grammar of CSS 2.1 ([CSS21], Appendix G):

filter_rule
  : FILTER_SYM S+ IDENT S* '{' S* group_rule_body '}' S*;
@{F}{I}{L}{T}{E}{R}   {return FILTER_SYM;}

group_rule_body as defined in [CSS3-CONDITIONAL].

Furthermore, the nested_statement rule [CSS3-CONDITIONAL] gets extended by adding "filter_rule".

11.3. Custom filter resources: the src descriptor

Name:	src
Value:	[ <uri> [format(<string>)]?]#
Initial:	N/A

The ‘src’ descriptor takes a comma separated list of resource references with an optional format function. The resource format is either determined by a provided custom filter format string with the format function, or by the MIME type of the resource (e.g. transfered MIME type from the resource providing server). If a format function is provided, then the passed string overrides the MIME type definition of the resource. The type of a customized filter effect depends on the format of the resources.

It is possible to reference custom filter resources in a document by a fragment identifier. The format may be identified by the context of the referenced resource. If the referenced resource is a ‘<script>’ element, the ‘type’ attribute defines the format of the content.

The following document from Mozilla describes how WebGL vertex and fragment shaders can be defined in <script> elements.

<script id="warp" type="x-shader/x-vertex" >
  <-- source code here -->
</script>
<style>
  @filter warp {
    src: url(#warp);
  }
</style>

Format strings defined by this specification:

String	Custom-filter Format	Common extensions
"x-shader/x-vertex"	WebGL 1.0 vertex shader	.vs
"x-shader/x-fragment"	WebGL 1.0 fragment shader	.fs

11.4. Custom filter parameters: the parameters descriptor

Name:	parameters
Value:	<param>#
Initial:	N/A

The list of parameters define variables, that get passed into the custom filter effect (e.g. parameters passed to a shader). Each parameter has an identifier. If a parameter with the same identifier occurs more then once in the list of parameters, the latest parameter definition overrides all previous definitions. A parameter definition can be overloaded by a parameter definition in the referencing custom filter function.

<param> = IDENT <param-value>

<param-value> = <transform-function>+ | <number>{1,4} | <array> |  <mat> | <color> | <URI>

<array> = array(<number>#)

<mat> = mat2(<number> [ , <number> ]{3,3}) | mat3(<number> [ , <number> ]{8,8}) | mat4(<number> [ , <number> ]{15,15})

array(<number>#)

Specifies an array of number values.

<color>

A CSS color value. (See [CSS3COLOR].)

<transform-function>

A CSS transform function value. (See [CSS3-TRANSFORMS].)

<URI>

A URL reference to an image source.

The following function definitions describe matrices in column-major order.

mat2(<number> [ , <number> ]{3,3})

Specifies a 2x2 homogeneous matrix of 4 values.

mat3(<number> [ , <number> ]{8,8})

Specifies a 3x3 homogeneous matrix of 9 values.

mat4(<number> [ , <number> ]{15,15})

Specifies a 4x4 homogeneous matrix of 16 values.

11.5. Custom filter geometry: the geometry descriptor

Name:	geometry
Value:	<geometry-shape>
Initial:	grid(1 1 attached)

<geometry-shape> = grid(<integer>{1,2} || [ detached | attached ]?)

grid(<integer>{1,2} || [ detached | attached ]?)

<integer>

One or two positive integers greater then zero indicate the additional number of vertex lines and columns that will make the vertex mesh. With the initial value of ‘1 1’ there is a single row and a single column, resulting in a four-vertices mesh (top-left, top-right, bottom-right, bottom-left). If the second parameter is not provided, it takes a value equal to the first. A value of ‘n m’ results in a vertex mesh that has n columns and m rows. This results in a total of (n + 1) * (m + 1) vertices. If one of the passed parameters is zero or negative, the UA must use the initial mesh.

The figure illustrates how a mesh of ‘6 6’ creates vertices passed to the vertex shader.

‘detached’

The geometry provided to the vertex shader is made of triangles which do not share adjacent edges' vertices. A value of ‘detached’ implies that the vertices are detached.

‘attached’

The geometry provided to the vertex shader is made of triangles which do not share adjacent edges' vertices. A value of ‘attached’ implies that the vertices are attached.

If no value for attachmeny of verices is specified, it computes to ‘attached’.

11.6. Custom filter compositing: the mix descriptor

Name:	mix
Value:	auto | [<blend-mode> || <composite-mode>]
Initial:	auto

‘auto’

The UA must follow the host language's recommendation.

<blend-mode>

Specifies blending mechanisms for the filter primitive. The host language must define the meaning.

<composite-mode>

Specifies composition mechanisms for the filter primitive. The host language must define the meaning.

11.7. Custom filter margins: the margin descriptor

Name:	margin
Value:	<margin-width>{1,4}
Initial:	auto
Computed Value:	the percentage as specified or the absolute length. A value of auto computes to 10% of the input Filter primitive subregion.

The ‘margin’ descriptor values and the input Filter primitive subregion define the filter primitive subregion of the custom filter primitive.

<margin-width> = <length> | <percentage> | auto

For the definition of the <margin-width> values see CSS Box Model [CSS21].

12. Custom Shaders

12.1. Introduction

With Custom Shaders, authors can manipulate the color and shape of a graphical element in granular ways. The following sections describe the host language Custom Shaders as extension for Custom Filter Functions.

12.2. Precedents

There are many precedents for shading languages, for example:

• OpenGL ES Shading Language (also known as GLSL ES) from WebGL
• HLSL Shading Language
• Adobe's Pixel Bender language
• Apple's CoreImage Filters

12.3. Recommended shading language

This document recommends the adoption of the subset of GLSL ES [GLSLES] defined in the WebGL 1.0 WEBGL] specification.

In particular, the same restrictions as defined in WebGL should apply to shaders for CSS:

• supported GLSL constructs.
• differences between WebGL and OpenGL ES 2.0 as it applies to shaders.

All the parameters specified in the <param> values (e.g., the custom-filter at-rule or the ‘custom()’ filter function) will be available as uniforms to the shader(s) referenced by the ‘shader’ property.

The group may consider applying further restrictions to the GLSL ES language to make it easier to write vertex and fragment shaders.

The OpenGL ES shading language provides a number of variables that can be passed to shaders, exchanged between shaders or set by shaders. In particular, a vertex shader can provide specific data to the fragment shader in the form of "varying" parameters (parameters that vary per pixel). The following sections describe particular variables that are assumed for the vertex and fragment shaders.

12.4. Integration into Custom Filter Functions

Custom Filter Function values have the following meaning for Custom Shaders:

Values for ‘mix’ descriptor

<blend-mode>

For fragment shaders, each pixel is blended with the mix-color by using one of the predefined blend modes and it's appropriate blend mode keyword (See [COMPOSITING]).

<composite-mode>

For fragment shaders, each pixel is composed with the mix-color by using one of the predefined alpha-compositing operators and it's appropriate alpha-compositing keyword (See [COMPOSITING]).

‘auto’

If the ‘mix’ descriptor value computes to ‘auto’, the effect is as if ‘normal source-atop’ was specified.

12.5. Shader Processing Model

This section illustrates the shader processing model as it applies to an element whose unfiltered rendering is shown in the figure below.

Element before applying shaders

Prior to the shader processing, the input of the filter primitive gets rendered into an off-screen image (the source texture). The off-screen size and position is controlled by the filter primitive subregion.

Source texture created by rendering
the element off-screen and adding filter primitive margins

An <feCustom> element or a ‘custom()’ filter function defines a custom filter primitive. The following figure illustrates its model.

The shader processing model

In a first step the source texture is used on a vertex mesh. By default, the vertex mesh has the position and size of the filter primitive subregion. In the following figure, the red markers represent the default vertices in the default vertex mesh. The diagonal line illustrate how the vertices define two triangles.

The default vertex mesh and its default vertices

The ‘geometry’ attribute on the <feCustom> element and the ‘geometry’ descriptor on the custom-filter at-rule give more granularity control over the vertex mesh.

A finer, custom vertex mesh

In a second step, the vertex mesh gets processed through the vertex shader, which produces a set of transformed vertices. These transformed vertices are the output as shown in the figure below.

Transformed vertices after applying the vertex shader

The third step is the rasterization step. The filter primitive invokes the fragment shader for every pixel location inside the vertex mesh to perform per pixel operation and produce the final pixel color at that vertex mesh location.

Transformed vertices after applying the vertex shader

Note that the fragment shader may be called several times for what corresponds to the same pixel coordinate on the output, for example when the vertex mesh folds over itself. Overlaying pixel values do neither composite nor blend. The pixel value with the least depth will be choosen.

The ‘mix’ descriptor provides basic functionalities for color manipulation like blending and alpha compositing on a fragment shader. The processing model of ‘mix’ is illustrated in the following figure:

fragmentShader: processing model for mix

Each color value passed to the fragment shader gets multiplied with the color matrix, a predefined fragment shader variable that represents a 4x4 matrix. The matrix is initialized to an identity matrix, but can be set by a fragment shader. The resulting color is the multiplied color.

The mix color is a second, predefined fragment shader variable and represents an ‘RGBA’ <color> value. The mix color can be set by the fragment shader. If not specified, the default value is transparent black. The ‘RGB’ channels of the multiplied color get blended with the ‘RGB’ channels of the mix color with the multiplied color as destination and the mix color as source [COMPOSITING]. The applied blend mode depends on the passed <blend-mode> parameter which is ‘normal’ by default. The result of the blending and the opacity of the mix color define the blended color.

The multiplied color and the mix color get composed using the alpha-compositing rules as described in the Compositing and Blending spec [COMPOSITING]. The applied alpha-compositing mode is specified by the passed <composite-mode> parameter and is ‘source-atop’ by default.

The last step, step 4, shows rasterized output. If the custom filter primitive is the last primitive in the filter chain, then this output is the filtered rendering of the element. Otherwise, the output of the primitive becomes the input to the next filter primitive using it.

12.6. Differences to GLSL

12.6.1. Fragment Shaders Differences with GLSL

A normal GLSL shader requires that the fragment shader computes a gl_FragColor value which is the color value for the processed fragment (pixel).

Because of the security restrictions, fragment shaders are not allowed to access rendered content pixel values directly. However, fragment shaders in this specification have the option to compute a value that is automatically mixed with the rendered content pixel values (but without ever providing direct access to these values to the shader code).

In the context of this specification, fragment shaders have the options to compute the following values:

• gl_FragColor. If the compositing and blending values for the ‘mix’ descriptor compute to ‘none’ the shader computes a gl_FragColor value. This may be useful, for example, to compute complex patterns.
• css_MixColor. If the compositing and blending values for the ‘mix’ descriptor do not compute to ‘none’, then the shader computes a mix color value that is composited with the rendered content as explained in the shaders processing model.
• css_ColorMatrix. If the compositing and blending values for the ‘mix’ descriptor do not compute to ‘none’, then the shader computes a color matrix value that is multiplied with the rendered content as explained in the shaders processing model.

The following example shows a fragment shader which computes a simple solid red color:

CSS

@filter red {
    src: url('simple.vs') format('x-shader/x-vertex'), url(simple.fs) format('x-shader/x-fragment');
}
#filtered-element {
    filter: custom(red);
}
      

simple.vs

  attribute vec4 a_position;
  void main()
  {        
      gl_Position = a_position;
  }

simple.fs

void main()
{  
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}

The following example shows a fragment shader which darkens the rendered content by computing a css_MixColor which is multiplied with the rendered content:

CSS

@filter darken {
    src: url('simple2.vs') format('x-shader/x-vertex'), url(simple2.fs) format('x-shader/x-fragment');
    mix: multiply;
}
#filtered-element {
    filter: custom(mix);
}
    

simple2.vs

  attribute vec4 a_position;
  void main()
  {        
      gl_Position = a_position;
  }

simple2.fs

  void main()
  {  
      css_MixColor = vec4(0.8, 0.8, 0.8, 1.0);
  }      

The following example shows a fragment shader which darkens the rendered content by computing a css_ColorMatrix which varies depending on the texture coordinate:

CSS

@filter colormatrix {
    src: url('simple.vs') format('x-shader/x-vertex'), url(simple3.fs) format('x-shader/x-fragment');
}
#filtered-element {
    filter: custom(colormatrix);
}
      

simple3.vs

  attribute vec4 a_position;
  varying vec2 v_texCoord;
  void main()
  {      
      v_texCoord = a_position.xy;  
      gl_Position = a_position;
  }

simple3.fs

varying vec2 v_texCoord;
void main()
{  
    float x = v_texCoord.x;
    css_ColorMatrix = mat4(
        vec4(x, x, x, x), // 1st column
        vec4(x, x, x, x), // 2nd column
        vec4(x, x, x, x), // 3rd column
        vec4(x, x, x, x), // 4th column
    );
}      

12.6.2. Vertex attribute variables

The following attribute variables are available to the vertex shader.

attribute variables	description
attribute vec4 a_position	The vertex coordinates in the Filter primitive subregion. Coordinates are normalized to the [0, 1] range along the x, y and z axis.
attribute vec3 a_triangleCoord	The x and y values provide the coordinate of the current ‘tile’ in the shader mesh. For example, (0, 0) for the top right tile in the mesh. The x and y values are in the [0, mesh columns] and [0, mesh rows] range, respectively. The z coordinate is computed according to the following figure. The z coordinate value is provided for each vertex and corresponding triangle. For example, for the bottom right vertex of the top triangle, the z coordinate will be 2. For the bottom right vertex of the bottom triangle, the z coordinate will be 4.

The a_triangleCoord.z value

12.6.3. Shader uniform variables

The following uniform variables are set to specific values by the user agent:

uniform variable	description
uniform vec2 u_textureSize	The input texture's size. Includes the filter margins. The texture size is given in the actual device pixels and incorporates the device pixel ratio.
uniform vec2 u_meshSize	The size of the current mesh in terms of tiles. The x coordinate provides the number of columns and the y coordinate provides the number of rows.

12.6.4. Other uniform variables: the CSS shaders parameters

When there parameters are passed to the custom filter function or the <feCustom> filter primitive, the user agent pass uniforms of the corresponding name and type to the shaders.

The following table shows the mapping between CSS shader parameters and uniform types.

CSS param type	GLSL uniform type
<color>	vec4
<number>{1,4}	float, vec2, vec3 or vec4
<array>	float[n]
<transform-function>+	mat4
mat2(<number> [ , <number> ]{3,3}) | mat3(<number> [ , <number> ]{8,8}) | mat4(<number> [ , <number> ]{15,15})	mat2, mat3 or mat4
<image-list>	sampler2D

The following code sample illustrates that mechanism.

  CSS
  @filter distort {
    src: url(distort.vs), url(tint.fs);
    parameters: distortAmount 0.5, lightVector 1.0 1.0 0.0, disp texture(disp.png);
  }
  .shaded {
      filter: custom(distort);
  }
  Shader (vertex or fragment)
  ...
  uniform float distortAmount;
  uniform vec3 lightVector;
  uniform sampler2D disp;
  uniform vec2 dispSize;
  ...

As illustrated in the example, for each <textureName> texture() parameter, an additional vec2 uniform is passed to the shaders with the size of the corresponding texture.

12.6.5. Default shaders

If no vertex shader is provided, the default one is as shown below.

  attribute vec4 a_position;
  void main()
  {        
      gl_Position = a_position;
  }

If no fragment shader is provided, the default one is shown below.

  void main()
  {  
  }

12.6.6. Texture access

If shaders access texture values outside the [0, 1] range on both axis, the returned value is a fully translucent black pixel.

13. The filter CSS <image> value

The filter() function produces a CSS <image> value. It has the following syntax:

13.1. filter() syntax

<filter> = filter(
  <image>, 
  none | <filter-function>+
)

The function takes two parameters. The first is a CSS <image> value. The second is the value of a ‘filter’ property. The function take the input image parameter and apply the filter rules, returning a processing image.

The filter functions may increase the dimension of the image in comparison to the original image. Does it influence the offset when passed to a CSS property?

14. Shorthands defined in terms of the <filter> element

Below are the equivalents for each of the filter functions expressed in terms of the ‘filter element’ element. The parameters from the function are labelled with brackets in the following style: [amount]. In the case of parameters that are percentage values, they are converted to real numbers.

14.1. grayscale

 <filter id="grayscale">
    <feColorMatrix type="matrix"
               values="(0.2126 + 0.7874 * [1 - amount]) (0.7152 - 0.7152 * [1 - amount]) (0.0722 - 0.0722 * [1 - amount]) 0 0
                       (0.2126 - 0.2126 * [1 - amount]) (0.7152 + 0.2848 * [1 - amount]) (0.0722 - 0.0722 * [1 - amount]) 0 0
                       (0.2126 - 0.2126 * [1 - amount]) (0.7152 - 0.7152 * [1 - amount]) (0.0722 + 0.9278 * [1 - amount]) 0 0
                       0 0 0 1 0"/>
  </filter> 

14.2. sepia

 <filter id="sepia">
    <feColorMatrix type="matrix"
               values="(0.393 + 0.607 * [1 - amount]) (0.769 - 0.769 * [1 - amount]) (0.189 - 0.189 * [1 - amount]) 0 0
                       (0.349 - 0.349 * [1 - amount]) (0.686 + 0.314 * [1 - amount]) (0.168 - 0.168 * [1 - amount]) 0 0
                       (0.272 - 0.272 * [1 - amount]) (0.534 - 0.534 * [1 - amount]) (0.131 + 0.869 * [1 - amount]) 0 0
                       0 0 0 1 0"/>
  </filter> 

14.3. saturate

 <filter id="saturate">
    <feColorMatrix type="saturate"
               values="(1 - [amount])"/>
  </filter> 

14.4. hue-rotate

 <filter id="hue-rotate">
    <feColorMatrix type="hueRotate"
               values="[angle]"/>
  </filter> 

14.5. invert

 <filter id="invert">
    <feComponentTransfer>
        <feFuncR type="table" tableValues="[amount] (1 - [amount])"/>
        <feFuncG type="table" tableValues="[amount] (1 - [amount])"/>
        <feFuncB type="table" tableValues="[amount] (1 - [amount])"/>
    </feComponentTransfer>
  </filter> 

14.6. opacity

 <filter id="opacity">
    <feComponentTransfer>
        <feFuncA type="table" tableValues="0 [amount]"/>
    </feComponentTransfer>
  </filter> 

14.7. brightness

 <filter id="brightness">
    <feComponentTransfer>
        <feFuncR type="linear" slope="[amount]"/>
        <feFuncG type="linear" slope="[amount]"/>
        <feFuncB type="linear" slope="[amount]"/>
    </feComponentTransfer>
  </filter> 

14.8. contrast

 <filter id="contrast">
    <feComponentTransfer>
        <feFuncR type="linear" slope="[amount]" intercept="-(0.5 * [amount] + 0.5)"/>
        <feFuncG type="linear" slope="[amount]" intercept="-(0.5 * [amount] + 0.5)"/>
        <feFuncB type="linear" slope="[amount]" intercept="-(0.5 * [amount] + 0.5)"/>
    </feComponentTransfer>
  </filter> 

14.9. blur

 <filter id="blur">
    <feGaussianBlur stdDeviation="[radius radius]">
  </filter> 

14.10. drop-shadow

 <filter id="drop-shadow">
    <feGaussianBlur in="[alpha-channel-of-input]" stdDeviation="[radius]"/>
    <feOffset dx="[offset-x]" dy="[offset-y]" result="offsetblur"/>
    <feFlood flood-color="[color]"/>
    <feComposite in2="offsetblur" operator="in"/>
    <feMerge>
      <feMergeNode/>
      <feMergeNode in="[input-image]"/>
    </feMerge>
  </filter> 

14.11. custom

  <filter id="custom">
    <feCustom mix="[blend-mode || composite-mode]" geometry="[geometry-shape]">
      <feCustomParam ident="[ident]" type="[type]" values="values"/>
      ...
      <feCustomSource src="[resource]" format="[format]"/>
      ...
    </feCustom>
  </filter> 

15. The ‘enable-background’ property

Name:	enable-background
Value:	accumulate | new
Initial:	accumulate
Applies to:	Typically elements that can contain renderable elements. language is responsible for defining the applicable set of elements. For SVG: container elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	no

The property which enables access to the background image is ‘enable-background’:

new

• Indicates that a new (i.e., initially transparent black) background image canvas is established and that (in effect) all children of the current container element element shall be rendered into the new background image canvas in addition to being rendered onto the target device.

accumulate (the initial/default value)

• If an ancestor container element element has a property value of ‘enable-background: new’, then all renderable child elements of the current container element element are rendered both onto the parent container element element's background image canvas and onto the target device.
• Otherwise, there is no current background image canvas, so it is only necessary to render graphics elements the renderable elements onto the target device. (No need to render to the background image canvas.)

The ‘enable-background’ property has no affect if the ‘isolation’ property has a value of ‘isolate’ [COMPOSITING]. The isolation group defined by the ‘isolation’ property will establish a new background image canvas.

Two possible pseudo input images for filter effects are BackgroundImage and BackgroundAlpha, which each represent an image snapshot of the canvas under the filter region at the time that the <filter> element is invoked. BackgroundImage represents both the color values and alpha channel of the canvas (i.e., RGBA pixel values), whereas BackgroundAlpha represents only the alpha channel.

Implementations will often need to maintain supplemental background image buffers in order to support the BackgroundImage and BackgroundAlpha pseudo input images. Sometimes, the background image buffers will contain an in-memory copy of the accumulated painting operations on the current canvas.

Because in-memory image buffers can take up significant system resources, content must explicitly indicate to the user agent that the document needs access to the background image before BackgroundImage and BackgroundAlpha pseudo input images can be used.

A background image is what's been rendered before the current element. The host language is responsible for defining what rendered before in this context means. For SVG, that uses the painter's algorithm, rendered before means all of the prior elements in pre order traversal previous to the element to which the filter is applied.

If a filter effect specifies either the BackgroundImage or the BackgroundAlpha pseudo input images and no ancestor container element element has a property value of ‘enable-background: new’, then the background image request is technically in error. Processing will proceed without interruption (i.e., no error message) and a transparent black image shall be provided in response to the request.

15.1. Accessing the background image in SVG

This section only applies to the SVG definition of enable-background.

Assume you have an element E in the document and that E has a series of ancestors A₁ (its immediate parent), A₂, etc. (Note: A₀ is E.) Each ancestor A_i will have a corresponding temporary background image offscreen buffer BUF_i. The contents of the background image available to a <filter> referenced by E is defined as follows:

• Find the element A_i with the smallest subscript i (including A₀=E) for which the ‘enable-background’ property has the value ‘new’.

  Note that if there is no such ancestor element, then the outermost element A_n will be chosen.

• For each A_i (from i=n to 1), initialize BUF_i to transparent black. Render all children of A_i up to but not including A_i-1 into BUF_i. The children are painted, then filtered, clipped, masked and composited using the various painting, filtering, clipping, masking and object opacity settings on the given child. Any filter effects, masking and group opacity that might be set on A_i do not apply when rendering the children of A_i into BUF_i.
  (Note that for the case of A₀=E, the graphical contents of E are not rendered into BUF₁ and thus are not part of the background image available to E. Instead, the graphical contents of E are available via the SourceGraphic and SourceAlpha pseudo input images.)
• Then, for each A_i (from i=1 to n-1), composite BUF_i into BUF_i+1.
• The accumulated result (i.e., BUF_n) represents the background image available to E.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
  "https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="13.5cm" height="2.7cm" viewBox="0 0 1350 270"
     xmlns="https://www.w3.org/2000/svg" version="1.1">
  <title>Example enable-background01</title>
  <desc>This test case shows five pictures which illustrate the rules
        for background image processing.</desc>
  <defs>
    <filter id="ShiftBGAndBlur" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter discards the SourceGraphic, if any, and just produces
        a result consisting of the BackgroundImage shifted down 125 units
        and then blurred.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" />
    </filter>
    <filter id="ShiftBGAndBlur_WithSourceGraphic" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter takes the BackgroundImage, shifts it down 125 units, blurs it,
        and then renders the SourceGraphic on top of the shifted/blurred background.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" result="blur" />
      <feMerge>
        <feMergeNode in="blur"/>
        <feMergeNode in="SourceGraphic"/>
      </feMerge>
    </filter>
  </defs>
  <g transform="translate(0,0)">
    <desc>The first picture is our reference graphic without filters.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
  <g enable-background="new" transform="translate(270,0)">
    <desc>The second adds an empty 'g' element which invokes ShiftBGAndBlur.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <g filter="url(#ShiftBGAndBlur)"/>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
  <g enable-background="new" transform="translate(540,0)">
    <desc>The third invokes ShiftBGAndBlur on the inner group.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g filter="url(#ShiftBGAndBlur)" opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
  <g enable-background="new" transform="translate(810,0)">
    <desc>The fourth invokes ShiftBGAndBlur on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
  <g enable-background="new" transform="translate(1080,0)">
    <desc>The fifth invokes ShiftBGAndBlur_WithSourceGraphic on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur_WithSourceGraphic)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
</svg>

Example of ‘enable-background’ in use

View this example as SVG (SVG-enabled browsers only)

The example above contains five parts, described as follows:

1. The first set is the reference graphic. The reference graphic consists of a red rectangle followed by a 50% transparent <g> element. Inside the <g> is a green circle that partially overlaps the rectangle and a a blue triangle that partially overlaps the circle. The three objects are then outlined by a rectangle stroked with a thin blue line. No filters are applied to the reference graphic.
2. The second set enables background image processing and adds an empty <g> element which invokes the ShiftBGAndBlur filter. This filter takes the current accumulated background image (i.e., the entire reference graphic) as input, shifts its offscreen down, blurs it, and then writes the result to the canvas. Note that the offscreen for the filter is initialized to transparent black, which allows the already rendered rectangle, circle and triangle to show through after the filter renders its own result to the canvas.
3. The third set enables background image processing and instead invokes the ShiftBGAndBlur filter on the inner <g> element. The accumulated background at the time the filter is applied contains only the red rectangle. Because the children of the inner <g> (i.e., the circle and triangle) are not part of the inner <g> element's background and because ShiftBGAndBlur ignores SourceGraphic, the children of the inner <g> do not appear in the result.
4. The fourth set enables background image processing and invokes the ShiftBGAndBlur on the <polygon> element that draws the triangle. The accumulated background at the time the filter is applied contains the red rectangle plus the green circle ignoring the effect of the ‘opacity’ property on the inner <g> element. (Note that the blurred green circle at the bottom does not let the red rectangle show through on its left side. This is due to ignoring the effect of the ‘opacity’ property.) Because the triangle itself is not part of the accumulated background and because ShiftBGAndBlur ignores SourceGraphic, the triangle does not appear in the result.
5. The fifth set is the same as the fourth except that filter ShiftBGAndBlur_WithSourceGraphic is invoked instead of ShiftBGAndBlur. ShiftBGAndBlur_WithSourceGraphic performs the same effect as ShiftBGAndBlur, but then renders the SourceGraphic on top of the shifted, blurred background image. In this case, SourceGraphic is the blue triangle; thus, the result is the same as in the fourth case except that the blue triangle now appears.

16. Integration with CSS Animations and CSS Transitions

The CSS ‘filter’ property is animatable. Interpolation happens between the filter functions only if the ‘filter’ values have the same number of filter functions, and the same functions appearing in the same order.

The CSS WG may define different fading transitions in the future.

16.1. Interpolating filter function parameters

All properties defined as animatable, provided they are one of the property types listed in CSS3 Transitions [CSS3-TRANSITIONS], can be animated.

16.2. Interpolating the shader-params component in the custom() function.

To interpolate between ‘parameters’ values in a custom() filter function or between <feCustomParam> attribute values, the user agent should interpolate between each of the parameter values according to its type. List of values need to be of the same length. Matrices need to be of the same dimension. Arrays need to be of the same size.

Interpolation between shader params only happens if all the other shader properties are identical: vertex shader, fragment shader, filter margins and vertex mesh.

<number>[wsp<number>{0-3}]	Interpolate between each of the values.
<true|false>[wsp<true|fals>{0-3}]	Interpolate between each of the values using a step function.
<array>	Interpolate between the array elements.
<transform-function>	Follows the CSS3 transform interpolation rules.
<mat>	Interpolate between the matrix components (applies to mat2, mat3 and mat4).

As with the ‘transform’ property, it is not possible to animate the different components of the custom() filter parameters on different timelines or with different keyframes. This is a generic issue of animating properties that have multiple components to them.

17. Security

The following description of the security model is not sufficient and detailed enough. See public-fx mailing list.

17.1. Rendered Content Access in custom filter primitives

Since a custom filter primitive is applying a processing operation on input values, it is important that no protected information leaks from that operation.

A study of the security issues has led to the requirement that vertex shaders and fragment shaders do not get access to the rendered content in order to prevent timing attacks.

If a custom filter primitive does not fulfill these requirements, the primitive is a pass through.

17.2. Origin Restrictions

Input to a filter effect must not include anything as input that would violate same origin restrictions. If cross-origin access is required, then the requested content should be explicitly marked with CORS data.

This restriction includes:

• Any <iframe> content
• Any images, either as content or via styling, that are not exposed with CORS
• Any tainted canvas
• Any cross-origin content referenced by <use>

For content that falls under this restriction, the filter has no affect. For example, a filter effect that is applying to a cross-origin ‘iframe’ element does not have any affect on this element.

18. DOM interfaces

18.1. Interface SVGFilterElement

The SVGFilterElement interface corresponds to the <filter> element.

interface SVGFilterElement : SVGElement {
  readonly attribute SVGAnimatedEnumeration filterUnits;
  readonly attribute SVGAnimatedEnumeration primitiveUnits;
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGAnimatedInteger filterResX;
  readonly attribute SVGAnimatedInteger filterResY;
  void setFilterRes(in unsigned long filterResX, in unsigned long filterResY);
  ImageData apply(in ImageData source);
};
SVGFilterElement implements SVGURIReference;
SVGFilterElement implements SVGUnitTypes;

Attributes:

filterUnits (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘filterUnits’ on the given <filter> element. Takes one of the constants defined in SVGUnitTypes.

primitiveUnits (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘primitiveUnits’ on the given <filter> element. Takes one of the constants defined in SVGUnitTypes.

x (readonly SVGAnimatedLength)

Corresponds to attribute ‘x’ on the given <filter> element.

y (readonly SVGAnimatedLength)

Corresponds to attribute ‘y’ on the given <filter> element.

width (readonly SVGAnimatedLength)

Corresponds to attribute ‘width’ on the given <filter> element.

height (readonly SVGAnimatedLength)

Corresponds to attribute ‘height’ on the given <filter> element.

filterResX (readonly SVGAnimatedInteger)

Corresponds to attribute ‘filterRes’ on the given <filter> element. Contains the X component of attribute ‘filterRes’.

filterResY (readonly SVGAnimatedInteger)

Corresponds to attribute ‘filterRes’ on the given <filter> element. Contains the Y component (possibly computed automatically) of attribute ‘filterRes’.

Operations:

void setFilterRes(in unsigned long filterResX, in unsigned long filterResY)

Sets the values for attribute ‘filterRes’.

Parameters

1. unsigned long filterResX
   The X component of attribute ‘filterRes’.
2. unsigned long filterResY
   The Y component of attribute ‘filterRes’.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR

Raised on an attempt to change the value of a readonly attribute.

ImageData apply(in ImageData source)

Applies the filter to the given ImageData object and returns the result.

Parameters

1. ImageData source
   The image to apply the filter to.

Returns

The result of the filter, see ImageData for how to construct this.

18.2. Interface SVGFilterPrimitiveStandardAttributes

This interface defines the set of DOM attributes that are common across the filter primitive interfaces.

[NoInterfaceObject]
interface SVGFilterPrimitiveStandardAttributes {
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGAnimatedString result;
};

Attributes:

x (readonly SVGAnimatedLength)

Corresponds to attribute ‘filter primitive/x’ on the given element.

y (readonly SVGAnimatedLength)

Corresponds to attribute ‘filter primitive/y’ on the given element.

width (readonly SVGAnimatedLength)

Corresponds to attribute ‘filter primitive/width’ on the given element.

height (readonly SVGAnimatedLength)

Corresponds to attribute ‘filter primitive/height’ on the given element.

result (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/result’ on the given element.

18.3. Interface SVGFEBlendElement

The SVGFEBlendElement interface corresponds to the <feBlend> element.

interface SVGFEBlendElement : SVGElement {
  // Blend Mode Types
  const unsigned short SVG_FEBLEND_MODE_UNKNOWN = 0;
  const unsigned short SVG_FEBLEND_MODE_NORMAL = 1;
  const unsigned short SVG_FEBLEND_MODE_MULTIPLY = 2;
  const unsigned short SVG_FEBLEND_MODE_SCREEN = 3;
  const unsigned short SVG_FEBLEND_MODE_DARKEN = 4;
  const unsigned short SVG_FEBLEND_MODE_LIGHTEN = 5;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedString in2;
  readonly attribute SVGAnimatedEnumeration mode;
};
SVGFEBlendElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Blend Mode Types”:

SVG_FEBLEND_MODE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_FEBLEND_MODE_NORMAL (unsigned short)

Corresponds to value ‘normal’.

SVG_FEBLEND_MODE_MULTIPLY (unsigned short)

Corresponds to value ‘multiply’.

SVG_FEBLEND_MODE_SCREEN (unsigned short)

Corresponds to value ‘screen’.

SVG_FEBLEND_MODE_DARKEN (unsigned short)

Corresponds to value ‘darken’.

SVG_FEBLEND_MODE_LIGHTEN (unsigned short)

Corresponds to value ‘lighten’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feBlend> element.

in2 (readonly SVGAnimatedString)

Corresponds to attribute ‘in2’ on the given <feBlend> element.

mode (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘mode’ on the given <feBlend> element. Takes one of the SVG_FEBLEND_MODE_* constants defined on this interface.

18.4. Interface SVGFEColorMatrixElement

The SVGFEColorMatrixElement interface corresponds to the <feColorMatrix> element.

interface SVGFEColorMatrixElement : SVGElement {
  // Color Matrix Types
  const unsigned short SVG_FECOLORMATRIX_TYPE_UNKNOWN = 0;
  const unsigned short SVG_FECOLORMATRIX_TYPE_MATRIX = 1;
  const unsigned short SVG_FECOLORMATRIX_TYPE_SATURATE = 2;
  const unsigned short SVG_FECOLORMATRIX_TYPE_HUEROTATE = 3;
  const unsigned short SVG_FECOLORMATRIX_TYPE_LUMINANCETOALPHA = 4;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedEnumeration type;
  readonly attribute SVGAnimatedNumberList values;
};
SVGFEColorMatrixElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Color Matrix Types”:

SVG_FECOLORMATRIX_TYPE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_FECOLORMATRIX_TYPE_MATRIX (unsigned short)

Corresponds to value ‘matrix’.

SVG_FECOLORMATRIX_TYPE_SATURATE (unsigned short)

Corresponds to value ‘saturate’.

SVG_FECOLORMATRIX_TYPE_HUEROTATE (unsigned short)

Corresponds to value ‘hueRotate’.

SVG_FECOLORMATRIX_TYPE_LUMINANCETOALPHA (unsigned short)

Corresponds to value ‘luminanceToAlpha’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feColorMatrix> element.

type (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘type’ on the given <feColorMatrix> element. Takes one of the SVG_FECOLORMATRIX_TYPE_* constants defined on this interface.

values (readonly SVGAnimatedNumberList)

Corresponds to attribute ‘values’ on the given <feColorMatrix> element.

18.5. Interface SVGFEComponentTransferElement

The SVGFEComponentTransferElement interface corresponds to the <feComponentTransfer> element.

interface SVGFEComponentTransferElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
};
SVGFEComponentTransferElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feComponentTransfer> element.

18.6. Interface SVGComponentTransferFunctionElement

This interface defines a base interface used by the component transfer function interfaces.

interface SVGComponentTransferFunctionElement : SVGElement {
  // Component Transfer Types
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_UNKNOWN = 0;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_IDENTITY = 1;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_TABLE = 2;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_DISCRETE = 3;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_LINEAR = 4;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_GAMMA = 5;
  readonly attribute SVGAnimatedEnumeration type;
  readonly attribute SVGAnimatedNumberList tableValues;
  readonly attribute SVGAnimatedNumber slope;
  readonly attribute SVGAnimatedNumber intercept;
  readonly attribute SVGAnimatedNumber amplitude;
  readonly attribute SVGAnimatedNumber exponent;
  readonly attribute SVGAnimatedNumber offset;
};

Constants in group “Component Transfer Types”:

SVG_FECOMPONENTTRANSFER_TYPE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_FECOMPONENTTRANSFER_TYPE_IDENTITY (unsigned short)

Corresponds to value ‘identity’.

SVG_FECOMPONENTTRANSFER_TYPE_TABLE (unsigned short)

Corresponds to value ‘table’.

SVG_FECOMPONENTTRANSFER_TYPE_DISCRETE (unsigned short)

Corresponds to value ‘discrete’.

SVG_FECOMPONENTTRANSFER_TYPE_LINEAR (unsigned short)

Corresponds to value ‘linear’.

SVG_FECOMPONENTTRANSFER_TYPE_GAMMA (unsigned short)

Corresponds to value ‘gamma’.

Attributes:

type (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘feComponentTransferFunction/type’ on the given element. Takes one of the SVG_FECOMPONENTTRANSFER_TYPE_* constants defined on this interface.

tableValues (readonly SVGAnimatedNumberList)

Corresponds to attribute ‘feComponentTransferFunction/tableValues’ on the given element.

slope (readonly SVGAnimatedNumber)

Corresponds to attribute ‘feComponentTransferFunction/slope’ on the given element.

intercept (readonly SVGAnimatedNumber)

Corresponds to attribute ‘feComponentTransferFunction/intercept’ on the given element.

amplitude (readonly SVGAnimatedNumber)

Corresponds to attribute ‘feComponentTransferFunction/amplitude’ on the given element.

exponent (readonly SVGAnimatedNumber)

Corresponds to attribute ‘feComponentTransferFunction/exponent’ on the given element.

offset (readonly SVGAnimatedNumber)

Corresponds to attribute ‘feComponentTransferFunction/offset’ on the given element.

18.7. Interface SVGFEFuncRElement

The SVGFEFuncRElement interface corresponds to the <feFuncR> element.

interface SVGFEFuncRElement : SVGComponentTransferFunctionElement {
};

18.8. Interface SVGFEFuncGElement

The SVGFEFuncRElement interface corresponds to the <feFuncG> element.

interface SVGFEFuncGElement : SVGComponentTransferFunctionElement {
};

18.9. Interface SVGFEFuncBElement

The SVGFEFuncBElement interface corresponds to the <feFuncB> element.

interface SVGFEFuncBElement : SVGComponentTransferFunctionElement {
};

18.10. Interface SVGFEFuncAElement

The SVGFEFuncAElement interface corresponds to the <feFuncA> element.

interface SVGFEFuncAElement : SVGComponentTransferFunctionElement {
};

18.11. Interface SVGFECompositeElement

The SVGFECompositeElement interface corresponds to the <feComposite> element.

interface SVGFECompositeElement : SVGElement {
  // Composite Operators
  const unsigned short SVG_FECOMPOSITE_OPERATOR_UNKNOWN = 0;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_OVER = 1;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_IN = 2;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_OUT = 3;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_ATOP = 4;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_XOR = 5;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_ARITHMETIC = 6;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedString in2;
  readonly attribute SVGAnimatedEnumeration operator;
  readonly attribute SVGAnimatedNumber k1;
  readonly attribute SVGAnimatedNumber k2;
  readonly attribute SVGAnimatedNumber k3;
  readonly attribute SVGAnimatedNumber k4;
};
SVGFECompositeElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Composite Operators”:

SVG_FECOMPOSITE_OPERATOR_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_FECOMPOSITE_OPERATOR_OVER (unsigned short)

Corresponds to value ‘over’.

SVG_FECOMPOSITE_OPERATOR_IN (unsigned short)

Corresponds to value ‘in’.

SVG_FECOMPOSITE_OPERATOR_OUT (unsigned short)

Corresponds to value ‘out’.

SVG_FECOMPOSITE_OPERATOR_ATOP (unsigned short)

Corresponds to value ‘atop’.

SVG_FECOMPOSITE_OPERATOR_XOR (unsigned short)

Corresponds to value ‘xor’.

SVG_FECOMPOSITE_OPERATOR_ARITHMETIC (unsigned short)

Corresponds to value ‘arithmetic’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feComposite> element.

in2 (readonly SVGAnimatedString)

Corresponds to attribute ‘in2’ on the given <feComposite> element.

operator (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘operator’ on the given <feComposite> element. Takes one of the SVG_FECOMPOSITE_OPERATOR_* constants defined on this interface.

k1 (readonly SVGAnimatedNumber)

Corresponds to attribute ‘k1’ on the given <feComposite> element.

k2 (readonly SVGAnimatedNumber)

Corresponds to attribute ‘k2’ on the given <feComposite> element.

k3 (readonly SVGAnimatedNumber)

Corresponds to attribute ‘k3’ on the given <feComposite> element.

k4 (readonly SVGAnimatedNumber)

Corresponds to attribute ‘k4’ on the given <feComposite> element.

18.12. Interface SVGFEConvolveMatrixElement

The SVGFEConvolveMatrixElement interface corresponds to the <feConvolveMatrix> element.

interface SVGFEConvolveMatrixElement : SVGElement {
  // Edge Mode Values
  const unsigned short SVG_EDGEMODE_UNKNOWN = 0;
  const unsigned short SVG_EDGEMODE_DUPLICATE = 1;
  const unsigned short SVG_EDGEMODE_WRAP = 2;
  const unsigned short SVG_EDGEMODE_NONE = 3;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedInteger orderX;
  readonly attribute SVGAnimatedInteger orderY;
  readonly attribute SVGAnimatedNumberList kernelMatrix;
  readonly attribute SVGAnimatedNumber divisor;
  readonly attribute SVGAnimatedNumber bias;
  readonly attribute SVGAnimatedInteger targetX;
  readonly attribute SVGAnimatedInteger targetY;
  readonly attribute SVGAnimatedEnumeration edgeMode;
  readonly attribute SVGAnimatedNumber kernelUnitLengthX;
  readonly attribute SVGAnimatedNumber kernelUnitLengthY;
  readonly attribute SVGAnimatedBoolean preserveAlpha;
};
SVGFEConvolveMatrixElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Edge Mode Values”:

SVG_EDGEMODE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_EDGEMODE_DUPLICATE (unsigned short)

Corresponds to value ‘duplicate’.

SVG_EDGEMODE_WRAP (unsigned short)

Corresponds to value ‘wrap’.

SVG_EDGEMODE_NONE (unsigned short)

Corresponds to value ‘none’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feConvolveMatrix> element.

orderX (readonly SVGAnimatedInteger)

Corresponds to attribute ‘order’ on the given <feConvolveMatrix> element.

orderY (readonly SVGAnimatedInteger)

Corresponds to attribute ‘order’ on the given <feConvolveMatrix> element.

kernelMatrix (readonly SVGAnimatedNumberList)

Corresponds to attribute ‘kernelMatrix’ on the given <feConvolveMatrix> element.

divisor (readonly SVGAnimatedNumber)

Corresponds to attribute ‘divisor’ on the given <feConvolveMatrix> element.

bias (readonly SVGAnimatedNumber)

Corresponds to attribute ‘bias’ on the given <feConvolveMatrix> element.

targetX (readonly SVGAnimatedInteger)

Corresponds to attribute ‘targetX’ on the given <feConvolveMatrix> element.

targetY (readonly SVGAnimatedInteger)

Corresponds to attribute ‘targetY’ on the given <feConvolveMatrix> element.

edgeMode (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘edgeMode’ on the given <feConvolveMatrix> element. Takes one of the SVG_EDGEMODE_* constants defined on this interface.

kernelUnitLengthX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feConvolveMatrix> element.

kernelUnitLengthY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feConvolveMatrix> element.

preserveAlpha (readonly SVGAnimatedBoolean)

Corresponds to attribute ‘preserveAlpha’ on the given <feConvolveMatrix> element.

18.13. Interface SVGFECustomElement

The SVGFECustomElement interface corresponds to the <feCustom> element.

interface SVGFECustomElement : SVGElement {
  readonly attribute SVGAnimatedString in;
  readonly attribute SVGAnimatedString geometry;
};
SVGFECustomElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feCustom> element.

geometry (readonly SVGAnimatedString)

Corresponds to attribute ‘geometry’ on the given <feCustom> element.

18.14. Interface SVGFECustomSourceElement

The SVGFECustomSourceElement interface corresponds to the <feCustomSource> element.

interface SVGFECustomSourceElement : SVGElement {
  readonly attribute SVGAnimatedString src;
  readonly attribute SVGAnimatedString format;
};

Attributes:

src (readonly SVGAnimatedString)

Corresponds to attribute ‘src’ on the given <feCustomSource> element.

format (readonly SVGAnimatedString)

Corresponds to attribute ‘format’ on the given <feCustomSource> element.

18.15. Interface SVGFECustomParamElement

The SVGFECustomParamElement interface corresponds to the <feCustomParam> element.

interface SVGFECustomParamElement : SVGElement {
  // Custom Parameter Types
  const unsigned short SVG_CUSTOM_PARAM_UNKNOWN = 0;
  const unsigned short SVG_CUSTOM_PARAM_NUMBER = 1;
  const unsigned short SVG_CUSTOM_PARAM_ARRAY = 2;
  const unsigned short SVG_CUSTOM_PARAM_VEC2 = 3;
  const unsigned short SVG_CUSTOM_PARAM_VEC3 = 4;
  const unsigned short SVG_CUSTOM_PARAM_VEC4 = 5;
  const unsigned short SVG_CUSTOM_PARAM_MAT2 = 6;
  const unsigned short SVG_CUSTOM_PARAM_MAT3 = 7;
  const unsigned short SVG_CUSTOM_PARAM_MAT4 = 8;
  const unsigned short SVG_CUSTOM_PARAM_COLOR = 9;
  const unsigned short SVG_CUSTOM_PARAM_TEXTURE = 10;
  const unsigned short SVG_CUSTOM_PARAM_TRANSFORM = 11;
  readonly attribute SVGAnimatedEnumeration type;
  readonly attribute SVGAnimatedString ident;
  readonly attribute SVGAnimatedNumberList values;
  readonly attribute SVGAnimatedString texture;
  readonly attribute SVGAnimatedColor color;
  readonly attribute SVGAnimatedTransformList transform;
};

Constants in group "Custom Parameter Types":

SVG_CUSTOM_PARAM_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_CUSTOM_PARAM_NUMBER (unsigned short)

Corresponds to value ‘number’.

SVG_CUSTOM_PARAM_ARRAY (unsigned short)

Corresponds to value ‘array’.

SVG_CUSTOM_PARAM_VEC2 (unsigned short)

Corresponds to value ‘vec2’.

SVG_CUSTOM_PARAM_VEC3 (unsigned short)

Corresponds to value ‘vec3’.

SVG_CUSTOM_PARAM_VEC4 (unsigned short)

Corresponds to value ‘vec4’.

SVG_CUSTOM_PARAM_MAT2 (unsigned short)

Corresponds to value ‘mat2’.

SVG_CUSTOM_PARAM_MAT3 (unsigned short)

Corresponds to value ‘mat3’.

SVG_CUSTOM_PARAM_MAT4 (unsigned short)

Corresponds to value ‘mat4’.

SVG_CUSTOM_PARAM_COLOR (unsigned short)

Corresponds to value ‘color’.

SVG_CUSTOM_PARAM_TEXTURE (unsigned short)

Corresponds to value ‘texture’.

SVG_CUSTOM_PARAM_TRANSFOMR (unsigned short)

Corresponds to value ‘transform’.

Attributes:

type (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘type’ on the given <feCustomParam> element.

ident (readonly SVGAnimatedString)

Corresponds to attribute ‘ident’ on the given <feCustomParam> element.

values (readonly SVGAnimatedNumberList)

Corresponds to attribute ‘values’ on the given <feCustomParam> element.

texture (readonly SVGAnimatedString)

Corresponds to attribute ‘texture’ on the given <feCustomParam> element.

color (readonly SVGAnimatedColor)

Corresponds to attribute ‘color’ on the given <feCustomParam> element.

transform (readonly SVGAnimatedTransformList)

Corresponds to attribute ‘transform’ on the given <feCustomParam> element.

18.16. Interface SVGFEDiffuseLightingElement

The SVGFEDiffuseLightingElement interface corresponds to the <feDiffuseLighting> element.

interface SVGFEDiffuseLightingElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber surfaceScale;
  readonly attribute SVGAnimatedNumber diffuseConstant;
  readonly attribute SVGAnimatedNumber kernelUnitLengthX;
  readonly attribute SVGAnimatedNumber kernelUnitLengthY;
};
SVGFEDiffuseLightingElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feDiffuseLighting> element.

surfaceScale (readonly SVGAnimatedNumber)

Corresponds to attribute ‘surfaceScale’ on the given <feDiffuseLighting> element.

diffuseConstant (readonly SVGAnimatedNumber)

Corresponds to attribute ‘diffuseConstant’ on the given <feDiffuseLighting> element.

kernelUnitLengthX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feDiffuseLighting> element.

kernelUnitLengthY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feDiffuseLighting> element.

18.17. Interface SVGFEDistantLightElement

The SVGFEDistantLightElement interface corresponds to the <feDistantLight> element.

interface SVGFEDistantLightElement : SVGElement {
  readonly attribute SVGAnimatedNumber azimuth;
  readonly attribute SVGAnimatedNumber elevation;
};

Attributes:

azimuth (readonly SVGAnimatedNumber)

Corresponds to attribute ‘azimuth’ on the given <feDistantLight> element.

elevation (readonly SVGAnimatedNumber)

Corresponds to attribute ‘elevation’ on the given <feDistantLight> element.

18.18. Interface SVGFEPointLightElement

The SVGFEPointLightElement interface corresponds to the <fePointLight> element.

interface SVGFEPointLightElement : SVGElement {
  readonly attribute SVGAnimatedNumber x;
  readonly attribute SVGAnimatedNumber y;
  readonly attribute SVGAnimatedNumber z;
};

Attributes:

x (readonly SVGAnimatedNumber)

Corresponds to attribute ‘x’ on the given <fePointLight> element.

y (readonly SVGAnimatedNumber)

Corresponds to attribute ‘y’ on the given <fePointLight> element.

z (readonly SVGAnimatedNumber)

Corresponds to attribute ‘z’ on the given <fePointLight> element.

18.19. Interface SVGFESpotLightElement

The SVGFESpotLightElement interface corresponds to the <feSpotLight> element.

interface SVGFESpotLightElement : SVGElement {
  readonly attribute SVGAnimatedNumber x;
  readonly attribute SVGAnimatedNumber y;
  readonly attribute SVGAnimatedNumber z;
  readonly attribute SVGAnimatedNumber pointsAtX;
  readonly attribute SVGAnimatedNumber pointsAtY;
  readonly attribute SVGAnimatedNumber pointsAtZ;
  readonly attribute SVGAnimatedNumber specularExponent;
  readonly attribute SVGAnimatedNumber limitingConeAngle;
};

Attributes:

x (readonly SVGAnimatedNumber)

Corresponds to attribute ‘x’ on the given <feSpotLight> element.

y (readonly SVGAnimatedNumber)

Corresponds to attribute ‘y’ on the given <feSpotLight> element.

z (readonly SVGAnimatedNumber)

Corresponds to attribute ‘z’ on the given <feSpotLight> element.

pointsAtX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘pointsAtX’ on the given <feSpotLight> element.

pointsAtY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘pointsAtY’ on the given <feSpotLight> element.

pointsAtZ (readonly SVGAnimatedNumber)

Corresponds to attribute ‘pointsAtZ’ on the given <feSpotLight> element.

specularExponent (readonly SVGAnimatedNumber)

Corresponds to attribute ‘specularExponent’ on the given <feSpotLight> element.

limitingConeAngle (readonly SVGAnimatedNumber)

Corresponds to attribute ‘limitingConeAngle’ on the given <feSpotLight> element.

18.20. Interface SVGFEDisplacementMapElement

The SVGFEDisplacementMapElement interface corresponds to the <feDisplacementMap> element.

interface SVGFEDisplacementMapElement : SVGElement {
  // Channel Selectors
  const unsigned short SVG_CHANNEL_UNKNOWN = 0;
  const unsigned short SVG_CHANNEL_R = 1;
  const unsigned short SVG_CHANNEL_G = 2;
  const unsigned short SVG_CHANNEL_B = 3;
  const unsigned short SVG_CHANNEL_A = 4;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedString in2;
  readonly attribute SVGAnimatedNumber scale;
  readonly attribute SVGAnimatedEnumeration xChannelSelector;
  readonly attribute SVGAnimatedEnumeration yChannelSelector;
};
SVGFEDisplacementMapElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Channel Selectors”:

SVG_CHANNEL_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_CHANNEL_R (unsigned short)

Corresponds to value ‘R’.

SVG_CHANNEL_G (unsigned short)

Corresponds to value ‘G’.

SVG_CHANNEL_B (unsigned short)

Corresponds to value ‘B’.

SVG_CHANNEL_A (unsigned short)

Corresponds to value ‘A’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feDisplacementMap> element.

in2 (readonly SVGAnimatedString)

Corresponds to attribute ‘in2’ on the given <feDisplacementMap> element.

scale (readonly SVGAnimatedNumber)

Corresponds to attribute ‘scale’ on the given <feDisplacementMap> element.

xChannelSelector (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘xChannelSelector’ on the given <feDisplacementMap> element. Takes one of the SVG_CHANNEL_* constants defined on this interface.

yChannelSelector (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘yChannelSelector’ on the given <feDisplacementMap> element. Takes one of the SVG_CHANNEL_* constants defined on this interface.

18.21. Interface SVGFEDropShadowElement

The SVGFEDropShadowElement interface corresponds to the <feDropShadow> element.

interface SVGFEDropShadowElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber dx;
  readonly attribute SVGAnimatedNumber dy;
  readonly attribute SVGAnimatedNumber stdDeviationX;
  readonly attribute SVGAnimatedNumber stdDeviationY;
  void setStdDeviation(in float stdDeviationX, in float stdDeviationY);
};
SVGFEDropShadowElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feDropShadow> element.

dx (readonly SVGAnimatedNumber)

Corresponds to attribute ‘dx’ on the given <feDropShadow> element.

dy (readonly SVGAnimatedNumber)

Corresponds to attribute ‘dy’ on the given <feDropShadow> element.

stdDeviationX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘stdDeviation’ on the given <feDropShadow> element. Contains the X component of attribute ‘stdDeviation’.

stdDeviationY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘stdDeviation’ on the given <feDropShadow> element. Contains the Y component (possibly computed automatically) of attribute ‘stdDeviation’.

Operations:

void setStdDeviation(in float stdDeviationX, in float stdDeviationY)

Sets the values for attribute ‘stdDeviation’.

Parameters

1. float stdDeviationX
   The X component of attribute ‘stdDeviation’.
2. float stdDeviationY
   The Y component of attribute ‘stdDeviation’.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR

Raised on an attempt to change the value of a readonly attribute.

18.22. Interface SVGFEFloodElement

The SVGFEFloodElement interface corresponds to the <feFlood> element.

interface SVGFEFloodElement : SVGElement {
};
SVGFEFloodElement implements SVGFilterPrimitiveStandardAttributes;

18.23. Interface SVGFEGaussianBlurElement

The SVGFEGaussianBlurElement interface corresponds to the <feGaussianBlur> element.

interface SVGFEGaussianBlurElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber stdDeviationX;
  readonly attribute SVGAnimatedNumber stdDeviationY;
  void setStdDeviation(in float stdDeviationX, in float stdDeviationY);
};
SVGFEGaussianBlurElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feGaussianBlur> element.

stdDeviationX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘stdDeviation’ on the given <feGaussianBlur> element. Contains the X component of attribute ‘stdDeviation’.

stdDeviationY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘stdDeviation’ on the given <feGaussianBlur> element. Contains the Y component (possibly computed automatically) of attribute ‘stdDeviation’.

Operations:

void setStdDeviation(in float stdDeviationX, in float stdDeviationY)

Sets the values for attribute ‘stdDeviation’.

Parameters

1. float stdDeviationX
   The X component of attribute ‘stdDeviation’.
2. float stdDeviationY
   The Y component of attribute ‘stdDeviation’.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR

Raised on an attempt to change the value of a readonly attribute.

18.24. Interface SVGFEImageElement

The SVGFEImageElement interface corresponds to the <feImage> element.

interface SVGFEImageElement : SVGElement {
  readonly attribute SVGAnimatedPreserveAspectRatio preserveAspectRatio;
};
SVGFEImageElement implements SVGFilterPrimitiveStandardAttributes;
SVGFEImageElement implements SVGURIReference;

Attributes:

preserveAspectRatio (readonly SVGAnimatedPreserveAspectRatio)

Corresponds to attribute ‘preserveAspectRatio’ on the given <feImage> element.

18.25. Interface SVGFEMergeElement

The SVGFEMergeElement interface corresponds to the <feMerge> element.

interface SVGFEMergeElement : SVGElement {
};
SVGFEMergeElement implements SVGFilterPrimitiveStandardAttributes;

18.26. Interface SVGFEMergeNodeElement

The SVGFEMergeNodeElement interface corresponds to the <feMergeNode> element.

interface SVGFEMergeNodeElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
};

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feMergeNode>element.

18.27. Interface SVGFEMorphologyElement

The SVGFEMorphologyElement interface corresponds to the <feMorphology> element.

interface SVGFEMorphologyElement : SVGElement {
  // Morphology Operators
  const unsigned short SVG_MORPHOLOGY_OPERATOR_UNKNOWN = 0;
  const unsigned short SVG_MORPHOLOGY_OPERATOR_ERODE = 1;
  const unsigned short SVG_MORPHOLOGY_OPERATOR_DILATE = 2;
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedEnumeration operator;
  readonly attribute SVGAnimatedNumber radiusX;
  readonly attribute SVGAnimatedNumber radiusY;
};
SVGFEMorphologyElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Morphology Operators”:

SVG_MORPHOLOGY_OPERATOR_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_MORPHOLOGY_OPERATOR_ERODE (unsigned short)

Corresponds to value ‘erode’.

SVG_MORPHOLOGY_OPERATOR_DILATE (unsigned short)

Corresponds to value ‘dilate’.

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feMorphology> element.

operator (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘operator’ on the given <feMorphology> element. Takes one of the SVG_MORPHOLOGY_OPERATOR_* constants defined on this interface.

radiusX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘radius’ on the given <feMorphology> element.

radiusY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘radius’ on the given <feMorphology> element.

18.28. Interface SVGFEOffsetElement

The SVGFEOffsetElement interface corresponds to the <feOffset> element.

interface SVGFEOffsetElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber dx;
  readonly attribute SVGAnimatedNumber dy;
};
SVGFEOffsetElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feOffset> element.

dx (readonly SVGAnimatedNumber)

Corresponds to attribute ‘dx’ on the given <feOffset> element.

dy (readonly SVGAnimatedNumber)

Corresponds to attribute ‘dy’ on the given <feOffset> element.

18.29. Interface SVGFESpecularLightingElement

The SVGFESpecularLightingElement interface corresponds to the <feSpecularLighting> element.

interface SVGFESpecularLightingElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber surfaceScale;
  readonly attribute SVGAnimatedNumber specularConstant;
  readonly attribute SVGAnimatedNumber specularExponent;
  readonly attribute SVGAnimatedNumber kernelUnitLengthX;
  readonly attribute SVGAnimatedNumber kernelUnitLengthY;
};
SVGFESpecularLightingElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feSpecularLighting> element.

surfaceScale (readonly SVGAnimatedNumber)

Corresponds to attribute ‘surfaceScale’ on the given <feSpecularLighting> element.

specularConstant (readonly SVGAnimatedNumber)

Corresponds to attribute ‘specularConstant’ on the given <feSpecularLighting> element.

specularExponent (readonly SVGAnimatedNumber)

Corresponds to attribute ‘specularExponent’ on the given <feSpecularLighting> element.

kernelUnitLengthX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feSpecularLighting> element.

kernelUnitLengthY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘kernelUnitLength’ on the given <feSpecularLighting> element.

18.30. Interface SVGFETileElement

The SVGFETileElement interface corresponds to the <feTile> element.

interface SVGFETileElement : SVGElement {
  readonly attribute SVGAnimatedString in1;
};
SVGFETileElement implements SVGFilterPrimitiveStandardAttributes;

Attributes:

in1 (readonly SVGAnimatedString)

Corresponds to attribute ‘filter primitive/in’ on the given <feTile> element.

18.31. Interface SVGFETurbulenceElement

The SVGFETurbulenceElement interface corresponds to the <feTurbulence> element.

interface SVGFETurbulenceElement : SVGElement {
  // Turbulence Types
  const unsigned short SVG_TURBULENCE_TYPE_UNKNOWN = 0;
  const unsigned short SVG_TURBULENCE_TYPE_FRACTALNOISE = 1;
  const unsigned short SVG_TURBULENCE_TYPE_TURBULENCE = 2;
  // Stitch Options
  const unsigned short SVG_STITCHTYPE_UNKNOWN = 0;
  const unsigned short SVG_STITCHTYPE_STITCH = 1;
  const unsigned short SVG_STITCHTYPE_NOSTITCH = 2;
  readonly attribute SVGAnimatedNumber baseFrequencyX;
  readonly attribute SVGAnimatedNumber baseFrequencyY;
  readonly attribute SVGAnimatedInteger numOctaves;
  readonly attribute SVGAnimatedNumber seed;
  readonly attribute SVGAnimatedEnumeration stitchTiles;
  readonly attribute SVGAnimatedEnumeration type;
};
SVGFETurbulenceElement implements SVGFilterPrimitiveStandardAttributes;

Constants in group “Turbulence Types”:

SVG_TURBULENCE_TYPE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_TURBULENCE_TYPE_FRACTALNOISE (unsigned short)

Corresponds to value ‘fractalNoise’.

SVG_TURBULENCE_TYPE_TURBULENCE (unsigned short)

Corresponds to value ‘turbulence’.

Constants in group “Stitch Options”:

SVG_STITCHTYPE_UNKNOWN (unsigned short)

The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.

SVG_STITCHTYPE_STITCH (unsigned short)

Corresponds to value ‘stitch’.

SVG_STITCHTYPE_NOSTITCH (unsigned short)

Corresponds to value ‘noStitch’.

Attributes:

baseFrequencyX (readonly SVGAnimatedNumber)

Corresponds to attribute ‘baseFrequency’ on the given <feTurbulence> element. Contains the X component of the ‘baseFrequency’ attribute.

baseFrequencyY (readonly SVGAnimatedNumber)

Corresponds to attribute ‘baseFrequency’ on the given <feTurbulence> element. Contains the Y component of the (possibly computed automatically) ‘baseFrequency’ attribute.

numOctaves (readonly SVGAnimatedInteger)

Corresponds to attribute ‘numOctaves’ on the given <feTurbulence> element.

seed (readonly SVGAnimatedNumber)

Corresponds to attribute ‘seed’ on the given <feTurbulence> element.

stitchTiles (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘stitchTiles’ on the given <feTurbulence> element. Takes one of the SVG_STITCHTYPE_* constants defined on this interface.

type (readonly SVGAnimatedEnumeration)

Corresponds to attribute ‘type’ on the given <feTurbulence> element. Takes one of the SVG_TURBULENCE_TYPE_* constants defined on this interface.

19. Conformance

Document conventions

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words “for example” or are set apart from the normative text with class="example", like this:

This is an example of an informative example.

Informative notes begin with the word “Note” and are set apart from the normative text with class="note", like this:

Note, this is an informative note.

Conformance classes

Conformance to this is defined for three conformance classes:

style sheet

A CSS style sheet.

renderer

A UA that interprets the semantics of a style sheet and renders documents that use them.

authoring tool

A UA that writes a style sheet.

A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module.

A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.)

An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module.

Partial implementations

So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.

Experimental implementations

To avoid clashes with future CSS features, the CSS 2.1 specification reserves a prefixed syntax for proprietary and experimental extensions to CSS.

Prior to a specification reaching the Candidate Recommendation stage in the W3C process, all implementations of a CSS feature are considered experimental. The CSS Working Group recommends that implementations use a vendor-prefixed syntax for such features, including those in W3C Working Drafts. This avoids incompatibilities with future changes in the draft.

Non-experimental implementations

Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec.

To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group.

Further information on submitting testcases and implementation reports can be found from on the CSS Working Group's website at https://www.w3.org/Style/CSS/Test/. Questions should be directed to the public-css-testsuite@w3.org mailing list.

20. References

Normative references

[COMPOSITING]

Rik Cabanier; Nikos Andronikos. Compositing and Blending 1.0. 16 August 2012. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2012/WD-compositing-20120816/

[CSS21]

Bert Bos; et al. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. 7 June 2011. W3C Recommendation. URL: https://www.w3.org/TR/2011/REC-CSS2-20110607

[CSS3-CONDITIONAL]

L. David Baron. CSS Conditional Rules Module Level 3. 4 April 2013. W3C Candidate Recommendation. (Work in progress.) URL: https://www.w3.org/TR/2013/CR-css3-conditional-20130404/

[CSS3-TRANSFORMS]

Simon Fraser; et al. CSS Transforms. 11 September 2012. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2012/WD-css3-transforms-20120911/

[CSS3-TRANSITIONS]

Dean Jackson; et al. CSS Transitions. 12 February 2013. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2013/WD-css3-transitions-20130212/

[CSS3BG]

Bert Bos; Elika J. Etemad; Brad Kemper. CSS Backgrounds and Borders Module Level 3. 24 July 2012. W3C Candidate Recommendation. (Work in progress.) URL: https://www.w3.org/TR/2012/CR-css3-background-20120724/

[CSS3COLOR]

Tantek Çelik; Chris Lilley; L. David Baron. CSS Color Module Level 3. 7 June 2011. W3C Recommendation. URL: https://www.w3.org/TR/2011/REC-css3-color-20110607

[CSSOM]

Anne van Kesteren. CSSOM. 12 July 2011. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2011/WD-cssom-20110712/

[RFC2119]

S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. Internet RFC 2119. URL: https://www.ietf.org/rfc/rfc2119.txt

[SVG11]

Erik Dahlström; et al. Scalable Vector Graphics (SVG) 1.1 (Second Edition). 16 August 2011. W3C Recommendation. URL: https://www.w3.org/TR/2011/REC-SVG11-20110816/

[GLSLES]

R. J. Simpson. The OpenGL® ES Shading Language. 12 May 2009. The Khronos Group Inc. URL: https://www.khronos.org/registry/gles/specs/2.0/GLSL_ES_Specification_1.0.17.pdf

[WEBGL]

C. Marrin. WebGL Specification Version 1.0. 10 February 2011. The Khronos Group Inc. URL: https://www.khronos.org/registry/webgl/specs/1.0/

[PORTERDUFF]

T. Porter, T. Duff. Compositing Digital Images. July 1984. SIGGRAPH `84 Conference Proceedings, Association for Computing Machinery, Volume 18, Number 3

Other references

Changes

The following significant changes were made since the 25 October 2012 Working Draft.

• Correction of brightness short hand filter.
• New syntax for Custom Filter function.
• Add at-function rule for Custom Filters.
• Allow Custom Filter function to be used as extension for future filter features.
• Remove unnecessary attributes and uniforms on shaders.
• Redefine origin of shader coordinate space to bottom left.
• Remove now unnecessary filter-margin properties.

See more detailed and longterm changes in the ChangeLog.

Property index

Property	Values	Initial	Applies to	Inh.	Percentages	Media
color-interpolation-filters	auto | sRGB | linearRGB	linearRGB	filter primitives	yes	N/A	visual
enable-background	accumulate | new	accumulate	Typically elements that can contain renderable elements. language is responsible for defining the applicable set of elements. For SVG: container elements	no	N/A	visual
feBlend
feColorMatrix
feComponentTransfer
feComposite
feConvolveMatrix
feCustom
feCustomParam
feCustomSource
feDiffuseLighting
feDisplacementMap
feDistantLight
feDropShadow
feFlood
feFuncA
feFuncB
feFuncG
feFuncR
feGaussianBlur
feImage
feMerge
feMergeNode
feMorphology
feOffset
fePointLight
feSpecularLighting
feSpotLight
feTile
feTurbulence
filter	none | <filter-function>+	none	All elements In SVG 1.1 it applies only to "container elements (except ‘mask’) and graphics elements"	no	N/A	visual
filter
flood-color	currentColor | <color> <icccolor>?	black	<feFlood> and <feDropShadow> elements	no	N/A	visual
flood-opacity	<number> | <percentage>	1	<feFlood> and <feDropShadow> elements	no	N/A	visual
lighting-color	currentColor | <color> <icccolor>?	white	<feDiffuseLighting> and <feSpecularLighting> elements	no	N/A	visual

Index

• <array>, 11.4.
• array(<number>#), 11.4.
• ‘attached’, 11.5.
• authoring tool, 19.
• ''auto''
  • 'mix' value, 11.6.
• blended color, 12.5.
• <blend-mode>, 11.6., 12.4.
• blur(<length>), 5.
• bounding client rect, 4.
• brightness(<number> | <percentage>), 5.
• <color>, 11.4.
• color-interpolation-filters, 9.
• color matrix, 12.5.
• <composite-mode>, 11.6., 12.4.
• contrast(<number> | <percentage>), 5.
• <custom-filter-type>, 11.1.
• custom(IDENT [, <param>]*), 5.
• ‘detached’, 11.5.
• drop-shadow([<length>{2,3} && <color>?]#), 5.
• enable-background, 15.
• feBlend, 8.4.
• feColorMatrix, 8.5.
• feComponentTransfer, 8.6.
• feComposite, 8.7.
• feConvolveMatrix, 8.8.
• feCustom, 8.9.
• feCustomParam, 8.9.
• feCustomSource, 8.9.
• feDiffuseLighting, 8.10.
• feDisplacementMap, 8.11.
• feDistantLight, 10.2.
• feDropShadow, 8.12.
• feFlood, 8.13.
• feFuncA, 8.6.
• feFuncB, 8.6.
• feFuncG, 8.6.
• feFuncR, 8.6.
• feGaussianBlur, 8.14.
• feImage, 8.15.
• feMerge, 8.16.
• feMergeNode, 8.16.
• feMorphology, 8.17.
• feOffset, 8.18.
• fePointLight, 10.3.
• feSpecularLighting, 8.19.
• feSpotLight, 10.4.
• feTile, 8.20.
• feTurbulence, 8.21.
• filter, 5., 6.
• <filter>, 13.1.
• <filter-function>, 5.
• filter primitive attributes, 4.
• filter primitive elements, 4.
• <filter-primitive-reference>, 8.2.
• filter primitives, 4.
• filter_rule, 11.2.
• flood-color, 8.13.1.
• flood-opacity, 8.13.2.
• geometry, 11.5.
• <geometry-shape>, 11.5.
• grayscale(<number> | <percentage>), 5.
• grid(<integer>{1,2} || [ detached | attached ]?), 11.5.
• group_rule_body, 11.2.
• hue-rotate(<angle>), 5.
• <integer>, 11.5.
• invert(<number> | <percentage>), 5.
• lighting-color, 10.5.
• light source, 10.1.
• light sources, 4.
• local coordinate system, 4.
• margin, 11.7.
• <margin-width>, 11.7.
• <mat>, 11.4.
• mat2(<number> [ , <number> ]{3,3}), 11.4.
• mat3(<number> [ , <number> ]{8,8}), 11.4.
• mat4(<number> [ , <number> ]{15,15}), 11.4.
• mix, 11.6.
• mix color, 12.5.
• multiplied color, 12.5.
• null filter, 4.
• object bounding box units, 4.
• opacity(<number> | <percentage>), 5.
• <param>, 11.4.
• parameters, 11.4.
• <param-value>, 11.4.
• renderer, 19.
• saturate(<number> | <percentage>), 5.
• sepia(<number> | <percentage>), 5.
• src, 11.3.
• style sheet
  • as conformance class, 19.
• transfer function elements, 4.
• transfer functions, 8.6.
• <transform-function>, 11.4.
• <URI>, 11.4.
• <URL>, 5.
• user coordinate system, 4.
• vertex mesh, 4.