feat: OpenCV extension with pure Python modules #20611

VadimLevin · 2021-08-26T10:53:43Z

This patch adds an ability to extend OpenCV with pure Python modules and functions.

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I agree to contribute to the project under Apache 2 License.
To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
The PR is proposed to proper branch
There is reference to original bug report and related work
There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
The feature is well documented and sample code can be built with the project CMake

alalek

It would be nice to eliminate _extra_py_code somehow, but it conflicts with cv2 submodules from binary extension (not a misc case, but gapi)

modules/python/common.cmake

modules/python/python3/CMakeLists.txt

modules/python/python3/extra_modules/CMakeLists.txt

modules/python/python3/extra_modules/misc/__init__.py

modules/python/package/cv2/_extra_py_code/__init__.py

VadimLevin · 2021-09-13T20:20:09Z

It would be nice to eliminate _extra_py_code somehow, but it conflicts with cv2 submodules from binary extension (not a misc case, but gapi)

I succeed in eliminating _extra_py_code, but unfortunately it is not possible when there is names collision between cv2 represented as a package (with __init__.py) and cv2 represented as C extension module. To achieve the expected result - when there is cv2 package with all functions from cv2 C module I had to rename cv2 .so library to _cv2.*.so. The same thing is done in CPython CSV module

When there is no clashed names the only thing left is load required submodules and packages in a proper order:

Populate package symbols dictionary of the cv2 package from the cv2 module symbols (including submodules info)
Load Python submodules.
If there is a corresponding native submodule - extend loaded submodule with the native functions and classes.

sys.modules after `cv2 is loaded:

>>> import cv2
>>> import sys
>>> {m: sys.modules[m] for m in filter(lambda k: "cv2" in k, sys.modules)}
{
'cv2.load_config_py3': <module 'cv2.load_config_py3' from '/opencv-dev/build/python_loader/cv2/load_config_py3.py'>, 
'_cv2.Error': <module '_cv2.Error'>, 
'_cv2.cuda': <module '_cv2.cuda'>, 
'_cv2.detail': <module '_cv2.detail'>, 
'_cv2.dnn': <module '_cv2.dnn'>, 
'_cv2.fisheye': <module '_cv2.fisheye'>, 
'_cv2.flann': <module '_cv2.flann'>, 
'_cv2.gapi': <module '_cv2.gapi'>, 
'_cv2.gapi.core': <module '_cv2.gapi.core'>,
 '_cv2.gapi.core.cpu': <module '_cv2.gapi.core.cpu'>,
 '_cv2.gapi.core.fluid': <module '_cv2.gapi.core.fluid'>, 
'_cv2.gapi.core.ocl': <module '_cv2.gapi.core.ocl'>,
 '_cv2.gapi.ie': <module '_cv2.gapi.ie'>,
 '_cv2.gapi.ie.detail': <module '_cv2.gapi.ie.detail'>, 
'_cv2.gapi.onnx': <module '_cv2.gapi.onnx'>, 
'_cv2.gapi.own': <module '_cv2.gapi.own'>, 
'_cv2.gapi.own.detail': <module '_cv2.gapi.own.detail'>, 
'_cv2.gapi.render': <module '_cv2.gapi.render'>,
 '_cv2.gapi.render.ocv': <module '_cv2.gapi.render.ocv'>,
 '_cv2.gapi.streaming': <module '_cv2.gapi.streaming'>, 
'_cv2.gapi.video': <module '_cv2.gapi.video'>, 
'_cv2.gapi.wip': <module '_cv2.gapi.wip'>, 
'_cv2.gapi.wip.draw': <module '_cv2.gapi.wip.draw'>,
 '_cv2.ipp': <module '_cv2.ipp'>, 
'_cv2.ml': <module '_cv2.ml'>,
 '_cv2.ocl': <module '_cv2.ocl'>,
 '_cv2.ogl': <module '_cv2.ogl'>,
 '_cv2.parallel': <module '_cv2.parallel'>,
 '_cv2.samples': <module '_cv2.samples'>, 
'_cv2.segmentation': <module '_cv2.segmentation'>, 
'_cv2.utils': <module '_cv2.utils'>,
 '_cv2.utils.fs': <module '_cv2.utils.fs'>,
 '_cv2.videoio_registry': <module '_cv2.videoio_registry'>, 
'_cv2': <module '_cv2' from '/opencv-dev/build/lib/python3/_cv2.cpython-38-x86_64-linux-gnu.so'>, 
'cv2.gapi': <module '_cv2.gapi' from '/opencv-dev/build/python_loader/cv2/gapi/__init__.py'>, 
'cv2.misc.version': <module 'cv2.misc.version' from '/opencv-dev/build/python_loader/cv2/misc/version.py'>, 
'cv2.misc': <module 'cv2.misc' from '/opencv-dev/build/python_loader/cv2/misc/__init__.py'>,
 'cv2': <module 'cv2' from '/opencv-dev/build/python_loader/cv2/__init__.py'>
}

alalek

We should move forward through small harmless steps

modules/python/common.cmake

alalek · 2021-09-14T03:13:10Z

modules/python/src2/cv2.cpp

@@ -27,7 +27,7 @@
 #pragma warning(pop)
 #endif

-#define MODULESTR "cv2"
+#define MODULESTR "_cv2"


This renaming is not harmless in general.
It makes sense to keep existed flow for current release series.

I believe it is not a problem to load whole package at once. No need to support on-demand loading of submodules for conflict "subnames" already existed in C binary extension.

BTW, we have discussions about "opencv" name for package in 5.0 scope.

alalek · 2021-09-14T03:42:48Z

modules/python/test/test_misc.py

+            raise unittest.SkipTest('Python 2.x is not supported')
+
+        self.assertEqual(cv.misc.get_ocv_version(), cv.__version__,
+                         "Can't get package version using Python misc module")


It is still not clear to me that problem we want to resolve here (except loading from filesystem).

See here: https://github.com/alalek/opencv/commits/test_20611

I don't quite understand this comment

Python package cv2 now can handle both Python and C extension modules properly without additional "subfolders" like "_extra_py_code".

VadimLevin · 2021-09-14T05:48:01Z

I've done some juggling with native modules and Python packages and looks like I achieved the desired result without renaming the .so library.
@alalek have a look, please.

After OpenCV package is loaded:

>>> import cv2
>>> import sys
>>> {m: sys.modules[m] for m in filter(lambda k: "cv2" in k, sys.modules)}
{
'cv2.load_config_py3': <module 'cv2.load_config_py3' from '/opencv-dev/build/python_loader/cv2/load_config_py3.py'>,
'cv2.Error': <module 'cv2.Error'>,
'cv2.cuda': <module 'cv2.cuda'>
'cv2.detail': <module 'cv2.detail'>,
'cv2.dnn': <module 'cv2.dnn'>,
'cv2.fisheye': <module 'cv2.fisheye'>,
'cv2.flann': <module 'cv2.flann'>,
 'cv2.gapi.core': <module 'cv2.gapi.core'>, 
'cv2.gapi.core.cpu': <module 'cv2.gapi.core.cpu'>,
 'cv2.gapi.core.fluid': <module 'cv2.gapi.core.fluid'>,
 'cv2.gapi.core.ocl': <module 'cv2.gapi.core.ocl'>,
 'cv2.gapi.ie': <module 'cv2.gapi.ie'>,
 'cv2.gapi.ie.detail': <module 'cv2.gapi.ie.detail'>,
 'cv2.gapi.onnx': <module 'cv2.gapi.onnx'>, 
'cv2.gapi.own': <module 'cv2.gapi.own'>, 
'cv2.gapi.own.detail': <module 'cv2.gapi.own.detail'>, 
'cv2.gapi.render': <module 'cv2.gapi.render'>,
 'cv2.gapi.render.ocv': <module 'cv2.gapi.render.ocv'>, 
'cv2.gapi.streaming': <module 'cv2.gapi.streaming'>, 
'cv2.gapi.video': <module 'cv2.gapi.video'>, 
'cv2.gapi.wip': <module 'cv2.gapi.wip'>,
 'cv2.gapi.wip.draw': <module 'cv2.gapi.wip.draw'>, 
'cv2.ipp': <module 'cv2.ipp'>, 
'cv2.ml': <module 'cv2.ml'>,
 'cv2.ocl': <module 'cv2.ocl'>, 
'cv2.ogl': <module 'cv2.ogl'>,
 'cv2.parallel': <module 'cv2.parallel'>,
 'cv2.samples': <module 'cv2.samples'>, 
'cv2.segmentation': <module 'cv2.segmentation'>,
 'cv2.utils': <module 'cv2.utils'>, 
'cv2.utils.fs': <module 'cv2.utils.fs'>,
 'cv2.videoio_registry': <module 'cv2.videoio_registry'>,
 'cv2.gapi': <module 'cv2.gapi' from '/opencv-dev/build/python_loader/cv2/gapi/__init__.py'>,
 'cv2.misc.version': <module 'cv2.misc.version' from '/opencv-dev/build/python_loader/cv2/misc/version.py'>, 
'cv2.misc': <module 'cv2.misc' from '/opencv-dev/build/python_loader/cv2/misc/__init__.py'>,
 'cv2': <module 'cv2' from '/opencv-dev/build/python_loader/cv2/__init__.py'>
}

VadimLevin · 2021-09-14T07:17:34Z

Something wrong with Win32 DNN tests: link . Are they flapping?

modules/python/package/cv2/__init__.py

alalek

Well done! Thank you 👍

…n-modules * feat: OpenCV extension with pure Python modules * feat: cv2 is now a Python package instead of extension module Python package cv2 now can handle both Python and C extension modules properly without additional "subfolders" like "_extra_py_code". * feat: can call native function from its reimplementation in Python

feat: OpenCV extension with pure Python modules

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VadimLevin added category: python bindings feature labels Aug 26, 2021

alalek reviewed Aug 27, 2021

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alalek reviewed Aug 30, 2021

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alalek mentioned this pull request Sep 3, 2021

python: cv.Mat wrapper over numpy.ndarray #20558

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alalek assigned VadimLevin Sep 8, 2021

VadimLevin force-pushed the dev/vlevin/pure-python-modules branch from 14ccf91 to 7f5b8ee Compare September 13, 2021 20:12

VadimLevin force-pushed the dev/vlevin/pure-python-modules branch from 7f5b8ee to ba70421 Compare September 13, 2021 20:32

alalek reviewed Sep 14, 2021

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feat: cv2 is now a Python package instead of extension module

15669fb

Python package cv2 now can handle both Python and C extension modules properly without additional "subfolders" like "_extra_py_code".

VadimLevin force-pushed the dev/vlevin/pure-python-modules branch from ba70421 to 15669fb Compare September 14, 2021 05:38

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feat: can call native function from its reimplementation in Python

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alalek approved these changes Sep 16, 2021

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alalek merged commit 3c89a28 into opencv:master Sep 18, 2021

alalek unassigned VadimLevin Sep 18, 2021

This was referenced Oct 15, 2021

cmake: update installation of python extra submodules #20885

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(5.x) Merge 4.x #20886

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opencv-alalek mentioned this pull request Feb 24, 2024

fix [use hasattr("cv2", "name") ,but first param is 'character string', #25079

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