Merge pull request #2464 from devanshbatra04:master

devanshbatra04 · web-flow · commit aba93d5fd5cc · 2020-04-19T12:16:05.000Z
Add Stroke Width Transform algorithm for Text Detection

* added SWTTextDetection code

* remove warnings from opencv_text compilation

* added bib for SWT Text Detection

* resolve initial pr suggestions

* change file name according to convention

* added optional OutputArray

* removed bug related to letter candidature

* added unit tests for stroke width transform text detection

* Added demo program

* made all minor edits required

* corrected findDataFilePath and removed manual allocation

* Added ArgumentParser

* corrected typo

* remove headers not allowed

* correct test case

* corrected float typecast warnings and test case

* remove final double correction and problematic test case

* test(swt): coding style

* finalminor bug corrections
diff --git a/modules/text/doc/text.bib b/modules/text/doc/text.bib
@@ -42,3 +42,11 @@ @inproceedings{LiaoSBWL17
   booktitle = {AAAI},
   year      = {2017}
 }
+@inproceedings{LiaoSBWL17,
+  author    = {Boris Epshtein and
+               Eyal Ofek and
+               Yonatan Wexler and},
+  title     = {Detecting Text in Natural Scenes with Stroke Width Transform},
+  booktitle = {CVPR},
+  year      = {2010}
+}
diff --git a/modules/text/include/opencv2/text.hpp b/modules/text/include/opencv2/text.hpp
@@ -42,6 +42,7 @@ the use of this software, even if advised of the possibility of such damage.
 #include "opencv2/text/erfilter.hpp"
 #include "opencv2/text/ocr.hpp"
 #include "opencv2/text/textDetector.hpp"
+#include "opencv2/text/swt_text_detection.hpp"
 
 /** @defgroup text Scene Text Detection and Recognition
 
diff --git a/modules/text/include/opencv2/text/swt_text_detection.hpp b/modules/text/include/opencv2/text/swt_text_detection.hpp
@@ -0,0 +1,24 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at https://opencv.org/license.html.
+
+#ifndef __OPENCV_TEXT_SWTTEXTDETECTOR_HPP__
+#define __OPENCV_TEXT_SWTTEXTDETECTOR_HPP__
+
+#include <opencv2/core.hpp>
+#include <vector>
+
+namespace cv {
+namespace text {
+/** @brief Applies the Stroke Width Transform operator followed by filtering of connected components of similar Stroke Widths to return letter candidates. It also chain them by proximity and size, saving the result in chainBBs.
+    @param input the input image with 3 channels.
+    @param result a vector of resulting bounding boxes where probability of finding text is high
+    @param dark_on_light a boolean value signifying whether the text is darker or lighter than the background, it is observed to reverse the gradient obtained from Scharr operator, and significantly affect the result.
+    @param draw an optional Mat of type CV_8UC3 which visualises the detected letters using bounding boxes.
+    @param chainBBs an optional parameter which chains the letter candidates according to heuristics in the paper and returns all possible regions where text is likely to occur.
+    */
+    CV_EXPORTS_W void detectTextSWT (InputArray input, CV_OUT std::vector<cv::Rect>& result, bool dark_on_light, OutputArray& draw=noArray(), OutputArray & chainBBs =noArray());
+}
+}
+
+#endif
diff --git a/modules/text/samples/textdetection_swt.cpp b/modules/text/samples/textdetection_swt.cpp
@@ -0,0 +1,89 @@
+// Sample code which demonstrates the working of
+// stroke width transform in the text module of OpenCV
+#include <opencv2/text.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/imgcodecs.hpp>
+
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <string>
+
+using namespace std;
+using namespace cv;
+
+static void help(const CommandLineParser& cmd, const string& errorMessage)
+{
+    cout << errorMessage << endl;
+    cout << "Avaible options:" << endl;
+    cmd.printMessage();
+}
+
+static bool fileExists (const string& filename)
+{
+    ifstream f(filename.c_str());
+    return f.good();
+}
+
+int main(int argc, const char * argv[])
+{
+    const char* keys =
+        "{help h usage ? |false | print this message }"
+        "{@image         |      | path to image }"
+        "{@darkOnLight   |false | indicates whether text to be extracted is dark on a light brackground. Defaults to false. }"
+        ;
+
+    CommandLineParser cmd(argc, argv, keys);
+
+    if(cmd.get<bool>("help"))
+    {
+        help(cmd, "Usage: ./textdetection_swt [options] \nExample: ./textdetection_swt scenetext_segmented_word03.jpg true");
+        return EXIT_FAILURE;
+    }
+
+    string filepath = cmd.get<string>("@image");
+
+    if (!fileExists(filepath)) {
+        help(cmd, "ERROR: Could not find the image file. Please check the path.");
+        return EXIT_FAILURE;
+    }
+
+    bool dark_on_light = cmd.get<bool>("@darkOnLight");
+
+    Mat image = imread(filepath, IMREAD_COLOR);
+
+    if (image.empty())
+    {
+        help(cmd, "ERROR: Could not load the image file");
+        return EXIT_FAILURE;
+    }
+
+    cout << "Starting SWT Text Detection Demo with dark_on_light variable set to " << dark_on_light << endl;
+
+    imshow("Input Image", image);
+    waitKey(1);
+
+    vector<cv::Rect> components;
+    Mat out;
+    vector<cv::Rect> regions;
+    cv::text::detectTextSWT(image, components, dark_on_light, out, regions);
+
+    imshow ("Letter Candidates", out);
+    waitKey(1);
+
+    cout << components.size() << " letter candidates found." << endl;
+
+    Mat image_copy = image.clone();
+
+    for (unsigned int i = 0; i < regions.size(); i++) {
+        rectangle(image_copy, regions[i], cv::Scalar(0, 0, 0), 3);
+    }
+    cout << regions.size() << " chains were obtained after merging suitable pairs" << endl;
+    cout << "Recognition finished. Press any key to exit..." << endl;
+
+    imshow ("Chains After Merging", image_copy);
+    waitKey();
+
+    return 0;
+}
diff --git a/modules/text/src/text_detector_swt.cpp b/modules/text/src/text_detector_swt.cpp
diff --git a/modules/text/test/test_detection_swt.cpp b/modules/text/test/test_detection_swt.cpp
