Added EDColor support to EdgeDrawing class.

Fixed a bug where params.PFmode = true caused incorrect edge detection results.
Updated edge_drawing.py to support the new EDColor feature.
Created a new edge_drawing_demo.cpp for demonstrating the EDColor feature.
Updated ximgproc.bib to include references for EDColor.
Added tests for PFmode and EDColor in test_fld.cpp.
Added CV_WRAP to Params::read and Params::write functions to expose them to Python bindings.

modules/ximgproc/doc/ximgproc.bib

@@ -388,6 +388,15 @@ @article{akinlar2013edcircles
   publisher={Elsevier}
 }
 
+@article{akinlar201782,
+  title = {ColorED: Color edge and segment detection by Edge Drawing (ED)},
+  author = {Cuneyt Akinlar and Cihan Topal},
+  journal = {Journal of Visual Communication and Image Representation},
+  volume = {44},
+  pages = {82-94},
+  year = {2017},
+  publisher={Academic Press}
+
 @article{loke2021accelerated,
   title={Accelerated superpixel image segmentation with a parallelized DBSCAN algorithm},
   author={Loke, Seng Cheong and MacDonald, Bruce A and Parsons, Matthew and W{\"u}nsche, Burkhard Claus},

modules/ximgproc/include/opencv2/ximgproc.hpp

@@ -83,18 +83,42 @@
 
     @defgroup ximgproc_fast_line_detector Fast line detector
 
-    @defgroup ximgproc_edge_drawing EdgeDrawing
-
-    EDGE DRAWING LIBRARY FOR GEOMETRIC FEATURE EXTRACTION AND VALIDATION
-
-    Edge Drawing (ED) algorithm is an proactive approach on edge detection problem. In contrast to many other existing edge detection algorithms which follow a subtractive
-    approach (i.e. after applying gradient filters onto an image eliminating pixels w.r.t. several rules, e.g. non-maximal suppression and hysteresis in Canny), ED algorithm
-    works via an additive strategy, i.e. it picks edge pixels one by one, hence the name Edge Drawing. Then we process those random shaped edge segments to extract higher level
-    edge features, i.e. lines, circles, ellipses, etc. The popular method of extraction edge pixels from the thresholded gradient magnitudes is non-maximal supression that tests
-    every pixel whether it has the maximum gradient response along its gradient direction and eliminates if it does not. However, this method does not check status of the
-    neighboring pixels, and therefore might result low quality (in terms of edge continuity, smoothness, thinness, localization) edge segments. Instead of non-maximal supression,
-    ED points a set of edge pixels and join them by maximizing the total gradient response of edge segments. Therefore it can extract high quality edge segments without need for
-    an additional hysteresis step.
+    @defgroup ximgproc_edge_drawing Edge Drawing
+
+    Edge Drawing (ED) algorithm for geometric feature extraction and validation.
+
+    The Edge Drawing (ED) algorithm is a proactive approach to the edge detection problem.
+    In contrast to many existing edge detection algorithms, which follow a subtractive
+    approach (i.e., applying gradient filters and eliminating pixels based on several rules,
+    such as non-maximal suppression and hysteresis in the Canny Edge Detector), the ED algorithm
+    operates via an additive strategy. It selects edge pixels one by one and connects them,
+    hence the name Edge Drawing.
+
+    ED offers several key advantages:
+
+    1. **Additive Strategy**: Instead of eliminating non-edge pixels after gradient filtering,
+    ED incrementally builds up edge segments by selecting and connecting pixels based on
+    their gradient response. This differs from traditional methods, which rely on
+    non-maximal suppression and hysteresis to filter out non-edge pixels.
+
+    2. **Edge Pixel Selection**: ED selects edge pixels by analyzing their local gradient
+    response, while also considering neighboring pixels. This results in smoother and
+    more continuous edge segments, as ED aims to maximize the overall gradient strength
+    along the edge segment.
+
+    3. **Edge Segment Formation**: Traditional methods, such as non-maximal suppression,
+    check whether a pixel has the maximum gradient response along its gradient direction,
+    eliminating it otherwise. However, this approach doesn't consider neighboring pixels,
+    often resulting in lower-quality edge segments. ED, on the other hand, joins a set of
+    edge pixels together by maximizing the total gradient response of the segment, leading
+    to high-quality, well-localized edges.
+
+    4. **Higher-Level Feature Extraction**: After forming edge segments, ED enables the
+    extraction of higher-level geometric features such as lines, circles, ellipses, and
+    other shapes, making it useful for tasks involving geometric feature extraction and validation.
+
+    The ED algorithm produces continuous, smooth, and localized edge segments, making it ideal
+    for applications requiring precise edge detection and geometric shape analysis.
 
     @defgroup ximgproc_fourier Fourier descriptors
 

modules/ximgproc/include/opencv2/ximgproc/edge_drawing.hpp

@@ -15,7 +15,7 @@ namespace ximgproc
 //! @addtogroup ximgproc_edge_drawing
 //! @{
 
-/** @brief Class implementing the ED (EdgeDrawing) @cite topal2012edge, EDLines @cite akinlar2011edlines, EDPF @cite akinlar2012edpf and EDCircles @cite akinlar2013edcircles algorithms
+/** @brief Class implementing the ED (EdgeDrawing) @cite topal2012edge, EDLines @cite akinlar2011edlines, EDPF @cite akinlar2012edpf, EDCircles @cite akinlar2013edcircles and ColorED @cite akinlar201782 algorithms.
 */
 
 class CV_EXPORTS_W EdgeDrawing : public Algorithm
@@ -66,13 +66,13 @@ class CV_EXPORTS_W EdgeDrawing : public Algorithm
         //! Default value is 1.3
         CV_PROP_RW double MaxErrorThreshold;
 
-        void read(const FileNode& fn);
-        void write(FileStorage& fs) const;
+        CV_WRAP void read(const FileNode& fn);
+        CV_WRAP void write(FileStorage& fs) const;
     };
 
-    /** @brief Detects edges in a grayscale image and prepares them to detect lines and ellipses.
+    /** @brief Detects edges in a grayscale or color image and prepares them to detect lines and ellipses.
 
-    @param src 8-bit, single-channel, grayscale input image.
+    @param src 8-bit, single-channel (CV_8UC1) or color (CV_8UC3, CV_8UC4) input image.
     */
     CV_WRAP virtual void detectEdges(InputArray src) = 0;
 

modules/ximgproc/samples/edge_drawing.py

@@ -1,7 +1,24 @@
 #!/usr/bin/python
 
 '''
-This example illustrates how to use cv.ximgproc.EdgeDrawing class.
+This example script illustrates how to use cv.ximgproc.EdgeDrawing class.
+
+It uses the OpenCV library to load an image, and then use the EdgeDrawing class
+to detect edges, lines, and ellipses. The detected features are then drawn and displayed.
+
+The main loop allows the user changing parameters of EdgeDrawing by pressing following keys:
+
+to toggle the grayscale conversion press 'space' key
+to increase MinPathLength value press '/' key
+to decrease MinPathLength value press '*' key
+to increase MinLineLength value press '+' key
+to decrease MinLineLength value press '-' key
+to toggle NFAValidation value press 'n' key
+to toggle PFmode value press 'p' key
+to save parameters to file press 's' key
+to load parameters from file press 'l' key
+
+The program exits when the Esc key is pressed.
 
 Usage:
     ed.py [<image_name>]
@@ -16,71 +33,117 @@
 import random as rng
 import sys
 
-rng.seed(12345)
-
-def main():
-    try:
-        fn = sys.argv[1]
-    except IndexError:
-        fn = 'board.jpg'
-
-    src = cv.imread(cv.samples.findFile(fn))
-    gray = cv.cvtColor(src, cv.COLOR_BGR2GRAY)
-    cv.imshow("source", src)
-
-    ssrc = src.copy()*0
+def EdgeDrawingDemo(src, ed, EDParams, convert_to_gray):
+    rng.seed(12345)
+    ssrc = np.zeros_like(src)
     lsrc = src.copy()
     esrc = src.copy()
 
-    ed = cv.ximgproc.createEdgeDrawing()
+    img_to_detect = cv.cvtColor(src, cv.COLOR_BGR2GRAY) if convert_to_gray else src
 
-    # you can change parameters (refer the documentation to see all parameters)
-    EDParams = cv.ximgproc_EdgeDrawing_Params()
-    EDParams.MinPathLength = 50     # try changing this value between 5 to 1000
-    EDParams.PFmode = False         # defaut value try to swich it to True
-    EDParams.MinLineLength = 10     # try changing this value between 5 to 100
-    EDParams.NFAValidation = True   # defaut value try to swich it to False
+    cv.imshow("source image", img_to_detect)
 
-    ed.setParams(EDParams)
+    print("")
+    print("convert_to_gray:", convert_to_gray)
+    print("MinPathLength:", EDParams.MinPathLength)
+    print("MinLineLength:", EDParams.MinLineLength)
+    print("PFmode:", EDParams.PFmode)
+    print("NFAValidation:", EDParams.NFAValidation)
+
+    tm = cv.TickMeter()
+    tm.start()
 
     # Detect edges
     # you should call this before detectLines() and detectEllipses()
-    ed.detectEdges(gray)
+    ed.detectEdges(img_to_detect)
 
     segments = ed.getSegments()
     lines = ed.detectLines()
     ellipses = ed.detectEllipses()
 
-    #Draw detected edge segments
-    for i in range(len(segments)):
-        color = (rng.randint(0,256), rng.randint(0,256), rng.randint(0,256))
-        cv.polylines(ssrc, [segments[i]], False, color, 1, cv.LINE_8)
+    tm.stop()
+
+    print("Detection time : {:.2f} ms. using the parameters above".format(tm.getTimeMilli()))
+
+    # Draw detected edge segments
+    for segment in segments:
+        color = (rng.randint(0, 256), rng.randint(0, 256), rng.randint(0, 256))
+        cv.polylines(ssrc, [segment], False, color, 1, cv.LINE_8)
 
     cv.imshow("detected edge segments", ssrc)
 
-    #Draw detected lines
-    if lines is not None: # Check if the lines have been found and only then iterate over these and add them to the image
+    # Draw detected lines
+    if lines is not None:  # Check if the lines have been found and only then iterate over these and add them to the image
         lines = np.uint16(np.around(lines))
-        for i in range(len(lines)):
-            cv.line(lsrc, (lines[i][0][0], lines[i][0][1]), (lines[i][0][2], lines[i][0][3]), (0, 0, 255), 1, cv.LINE_AA)
+        for line in lines:
+            cv.line(lsrc, (line[0][0], line[0][1]), (line[0][2], line[0][3]), (0, 0, 255), 1, cv.LINE_AA)
 
     cv.imshow("detected lines", lsrc)
 
-    #Draw detected circles and ellipses
-    if ellipses is not None: # Check if circles and ellipses have been found and only then iterate over these and add them to the image
-        for i in range(len(ellipses)):
-            center = (int(ellipses[i][0][0]), int(ellipses[i][0][1]))
-            axes = (int(ellipses[i][0][2])+int(ellipses[i][0][3]),int(ellipses[i][0][2])+int(ellipses[i][0][4]))
-            angle = ellipses[i][0][5]
-            color = (0, 0, 255)
-            if ellipses[i][0][2] == 0:
-                color = (0, 255, 0)
-            cv.ellipse(esrc, center, axes, angle,0, 360, color, 2, cv.LINE_AA)
+    # Draw detected circles and ellipses
+    if ellipses is not None:  # Check if circles and ellipses have been found and only then iterate over these and add them to the image
+        for ellipse in ellipses:
+            center = (int(ellipse[0][0]), int(ellipse[0][1]))
+            axes = (int(ellipse[0][2] + ellipse[0][3]), int(ellipse[0][2] + ellipse[0][4]))
+            angle = ellipse[0][5]
+
+            color = (0, 255, 0) if ellipse[0][2] == 0 else (0, 0, 255)
+
+            cv.ellipse(esrc, center, axes, angle, 0, 360, color, 2, cv.LINE_AA)
 
     cv.imshow("detected circles and ellipses", esrc)
-    cv.waitKey(0)
-    print('Done')
 
+def main():
+    try:
+        fn = sys.argv[1]
+    except IndexError:
+        fn = 'board.jpg'
+    src = cv.imread(cv.samples.findFile(fn))
+    if src is None:
+        print("Error loading image")
+        return
+
+    ed = cv.ximgproc.createEdgeDrawing()
+
+    # Set parameters (refer to the documentation for all parameters)
+    EDParams = cv.ximgproc_EdgeDrawing_Params()
+    EDParams.MinPathLength = 10     # try changing this value by pressing '/' and '*' keys
+    EDParams.MinLineLength = 10     # try changing this value by pressing '+' and '-' keys
+    EDParams.PFmode = False         # default value is False, try switching by pressing 'p' key
+    EDParams.NFAValidation = True   # default value is True, try switching by pressing 'n' key
+
+    convert_to_gray = True
+    key = 0
+
+    while key != 27:
+        ed.setParams(EDParams)
+        EdgeDrawingDemo(src, ed, EDParams, convert_to_gray)
+        key = cv.waitKey()
+        if key == 32:  # space key
+            convert_to_gray = not convert_to_gray
+        if key == 112: # 'p' key
+            EDParams.PFmode = not EDParams.PFmode
+        if key == 110: # 'n' key
+            EDParams.NFAValidation = not EDParams.NFAValidation
+        if key == 43: # '+' key
+            EDParams.MinLineLength = EDParams.MinLineLength + 5
+        if key == 45: # '-' key
+            EDParams.MinLineLength = max(0, EDParams.MinLineLength - 5)
+        if key == 47: # '/' key
+            EDParams.MinPathLength = EDParams.MinPathLength + 20
+        if key == 42: # '*' key
+            EDParams.MinPathLength = max(0, EDParams.MinPathLength - 20)
+        if key == 115: # 's' key
+            fs = cv.FileStorage("ed-params.xml",cv.FileStorage_WRITE)
+            EDParams.write(fs)
+            fs.release()
+            print("parameters saved to ed-params.xml")
+        if key == 108: # 'l' key
+            fs = cv.FileStorage("ed-params.xml",cv.FileStorage_READ)
+            if fs.isOpened():
+                EDParams.read(fs.root())
+                fs.release()
+                print("parameters loaded from ed-params.xml")
 
 if __name__ == '__main__':
     print(__doc__)