Add DistanceTransform and Watershed

ROADMAP.md

@@ -63,11 +63,11 @@ Your pull requests will be greatly appreciated!
 
     - [ ] **Miscellaneous Image Transformations - WORK STARTED** The following functions still need implementation:
         - [ ] [cvtColorTwoPlane](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga8e873314e72a1a6c0252375538fbf753)
-        - [ ] [distanceTransform](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga8a0b7fdfcb7a13dde018988ba3a43042)
+        - [X] [distanceTransform](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga8a0b7fdfcb7a13dde018988ba3a43042)
         - [ ] [floodFill](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#gaf1f55a048f8a45bc3383586e80b1f0d0)
         - [ ] [grabCut](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga909c1dda50efcbeaa3ce126be862b37f)
         - [ ] [integral](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga97b87bec26908237e8ba0f6e96d23e28)
-        - [ ] [watershed](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga3267243e4d3f95165d55a618c65ac6e1)
+        - [X] [watershed](https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga3267243e4d3f95165d55a618c65ac6e1)
 
     - [ ] **Drawing Functions - WORK STARTED** The following functions still need implementation:
         - [ ] [clipLine](https://docs.opencv.org/master/d6/d6e/group__imgproc__draw.html#gaf483cb46ad6b049bc35ec67052ef1c2c)
@@ -81,8 +81,8 @@ Your pull requests will be greatly appreciated!
     - [ ] Planar Subdivision
     - [ ] **Histograms  - WORK STARTED** The following functions still need implementation:
         - [ ] [calcBackProject](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#ga3a0af640716b456c3d14af8aee12e3ca)
-        - [ ] [calcHist](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#ga4b2b5fd75503ff9e6844cc4dcdaed35d)
-        - [ ] [compareHist](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#gaf4190090efa5c47cb367cf97a9a519bd)
+        - [X] [calcHist](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#ga4b2b5fd75503ff9e6844cc4dcdaed35d)
+        - [X] [compareHist](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#gaf4190090efa5c47cb367cf97a9a519bd)
         - [ ] [EMD](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#ga902b8e60cc7075c8947345489221e0e0)
         - [ ] [wrapperEMD](https://docs.opencv.org/master/d6/dc7/group__imgproc__hist.html#ga31fdda0864e64ca6b9de252a2611758b)
 

imgproc.cpp

@@ -115,6 +115,10 @@ void Dilate(Mat src, Mat dst, Mat kernel) {
     cv::dilate(*src, *dst, *kernel);
 }
 
+void DistanceTransform(Mat src, Mat dst, Mat labels, int distanceType, int maskSize, int labelType) {
+    cv::distanceTransform(*src, *dst, *labels, distanceType, maskSize, labelType);
+}
+
 void Erode(Mat src, Mat dst, Mat kernel) {
     cv::erode(*src, *dst, *kernel);
 }
@@ -432,6 +436,10 @@ void WarpPerspective(Mat src, Mat dst, Mat m, Size dsize) {
     cv::warpPerspective(*src, *dst, *m, sz);
 }
 
+void Watershed(Mat image, Mat markers) {
+    cv::watershed(*image, *markers);
+}
+
 void ApplyColorMap(Mat src, Mat dst, int colormap) {
     cv::applyColorMap(*src, *dst, colormap);
 }

imgproc.go

@@ -234,6 +234,41 @@ func Dilate(src Mat, dst *Mat, kernel Mat) {
 	C.Dilate(src.p, dst.p, kernel.p)
 }
 
+// DistanceTransformLabelTypes are the types of the DistanceTransform algorithm flag
+type DistanceTransformLabelTypes int
+
+const (
+	// DistanceLabelCComp assigns the same label to each connected component of zeros in the source image
+	// (as well as all the non-zero pixels closest to the connected component).
+	DistanceLabelCComp DistanceTransformLabelTypes = 0
+
+	// DistanceLabelPixel assigns its own label to each zero pixel (and all the non-zero pixels closest to it).
+	DistanceLabelPixel
+)
+
+// DistanceTransformMasks are the marsk sizes for distance transform
+type DistanceTransformMasks int
+
+const (
+	// DistanceMask3 is a mask of size 3
+	DistanceMask3 DistanceTransformMasks = 0
+
+	// DistanceMask5 is a mask of size 3
+	DistanceMask5
+
+	// DistanceMaskPrecise is not currently supported
+	DistanceMaskPrecise
+)
+
+// DistanceTransform Calculates the distance to the closest zero pixel for each pixel of the source image.
+//
+// For further details, please see:
+// https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga8a0b7fdfcb7a13dde018988ba3a43042
+//
+func DistanceTransform(src Mat, dst *Mat, labels *Mat, distType DistanceTypes, maskSize DistanceTransformMasks, labelType DistanceTransformLabelTypes) {
+	C.DistanceTransform(src.p, dst.p, labels.p, C.int(distType), C.int(maskSize), C.int(labelType))
+}
+
 // Erode erodes an image by using a specific structuring element.
 //
 // For further details, please see:
@@ -1316,6 +1351,14 @@ func WarpPerspective(src Mat, dst *Mat, m Mat, sz image.Point) {
 	C.WarpPerspective(src.p, dst.p, m.p, pSize)
 }
 
+// Watershed performs a marker-based image segmentation using the watershed algorithm.
+//
+// For further details, please see:
+// https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#ga3267243e4d3f95165d55a618c65ac6e1
+func Watershed(image Mat, markers *Mat) {
+	C.Watershed(image.p, markers.p)
+}
+
 // ColormapTypes are the 12 GNU Octave/MATLAB equivalent colormaps.
 //
 // For further details, please see:

imgproc.h

@@ -29,6 +29,7 @@ void Blur(Mat src, Mat dst, Size ps);
 void BoxFilter(Mat src, Mat dst, int ddepth, Size ps);
 void SqBoxFilter(Mat src, Mat dst, int ddepth, Size ps);
 void Dilate(Mat src, Mat dst, Mat kernel);
+void DistanceTransform(Mat src, Mat dst, Mat labels, int distanceType, int maskSize, int labelType);
 void Erode(Mat src, Mat dst, Mat kernel);
 void MatchTemplate(Mat image, Mat templ, Mat result, int method, Mat mask);
 struct Moment Moments(Mat src, bool binaryImage);
@@ -84,6 +85,7 @@ void WarpAffine(Mat src, Mat dst, Mat rot_mat, Size dsize);
 void WarpAffineWithParams(Mat src, Mat dst, Mat rot_mat, Size dsize, int flags, int borderMode,
                           Scalar borderValue);
 void WarpPerspective(Mat src, Mat dst, Mat m, Size dsize);
+void Watershed(Mat image, Mat markers);
 void ApplyColorMap(Mat src, Mat dst, int colormap);
 void ApplyCustomColorMap(Mat src, Mat dst, Mat colormap);
 Mat GetPerspectiveTransform(Contour src, Contour dst);

imgproc_test.go

@@ -222,6 +222,33 @@ func TestDilate(t *testing.T) {
 	}
 }
 
+func TestDistanceTransform(t *testing.T) {
+	img := IMRead("images/face-detect.jpg", IMReadColor)
+	if img.Empty() {
+		t.Error("Invalid read of Mat in DistanceTransform test")
+	}
+	defer img.Close()
+
+	gray := NewMat()
+	defer gray.Close()
+	CvtColor(img, &gray, ColorBGRToGray)
+
+	threshImg := NewMat()
+	defer threshImg.Close()
+	Threshold(gray, &threshImg, 25, 255, ThresholdBinary)
+
+	dest := NewMat()
+	defer dest.Close()
+
+	labels := NewMat()
+	defer labels.Close()
+
+	DistanceTransform(threshImg, &dest, &labels, DistL2, DistanceMask3, DistanceLabelCComp)
+	if dest.Empty() || dest.Rows() != img.Rows() || img.Cols() != dest.Cols() {
+		t.Error("Invalid DistanceTransform test")
+	}
+}
+
 func TestMatchTemplate(t *testing.T) {
 	imgScene := IMRead("images/face.jpg", IMReadGrayScale)
 	if imgScene.Empty() {
@@ -1100,6 +1127,31 @@ func TestWarpAffineWithParamsGocvLogo(t *testing.T) {
 	}
 }
 
+func TestWatershed(t *testing.T) {
+	src := IMRead("images/gocvlogo.jpg", IMReadUnchanged)
+	if src.Empty() {
+		t.Error("Invalid read of Mat in Watershed test")
+	}
+	defer src.Close()
+
+	gray := NewMat()
+	defer gray.Close()
+	CvtColor(src, &gray, ColorBGRToGray)
+
+	imgThresh := NewMat()
+	defer imgThresh.Close()
+	Threshold(gray, &imgThresh, 5, 50, ThresholdOtsu+ThresholdBinary)
+
+	markers := NewMat()
+	defer markers.Close()
+	_ = ConnectedComponents(imgThresh, &markers)
+
+	Watershed(src, &markers)
+	if markers.Empty() || src.Cols() != markers.Cols() || src.Rows() != markers.Rows() {
+		t.Error("Invalid Watershed test")
+	}
+}
+
 func TestApplyColorMap(t *testing.T) {
 	type args struct {
 		colormapType ColormapTypes