From 6f4160c0140c8ef88d777ba2ee5a605bf345de64 Mon Sep 17 00:00:00 2001
From: Alexander Panov <alexander.panov@xperience.ai>
Date: Tue, 24 Aug 2021 22:29:40 +0300
Subject: [PATCH] Merge pull request #20584 from
 AleksandrPanov:fix_HoughCircles_ALT_dimensions

Fix hough circles alt dimensions

* fix OutputArray _circles dimensions

* add houghcircles_alt test

* fix warnings

* add shape assert

* change asserts
---
 modules/imgproc/src/hough.cpp            |  6 ++-
 modules/python/test/test_houghcircles.py | 47 ++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/modules/imgproc/src/hough.cpp b/modules/imgproc/src/hough.cpp
index 79f34521e8..5c78c94983 100644
--- a/modules/imgproc/src/hough.cpp
+++ b/modules/imgproc/src/hough.cpp
@@ -2301,14 +2301,16 @@ static void HoughCircles( InputArray _image, OutputArray _circles,
                 std::vector<Vec4f> cw(ncircles);
                 for( i = 0; i < ncircles; i++ )
                     cw[i] = GetCircle4f(circles[i]);
-                Mat(cw).copyTo(_circles);
+                if (ncircles > 0)
+                    Mat(1, (int)ncircles, cv::traits::Type<Vec4f>::value, &cw[0]).copyTo(_circles);
             }
             else if( type == CV_32FC3 )
             {
                 std::vector<Vec3f> cwow(ncircles);
                 for( i = 0; i < ncircles; i++ )
                     cwow[i] = GetCircle(circles[i]);
-                Mat(cwow).copyTo(_circles);
+                if (ncircles > 0)
+                    Mat(1, (int)ncircles, cv::traits::Type<Vec3f>::value, &cwow[0]).copyTo(_circles);
             }
             else
                 CV_Error(Error::StsError, "Internal error");
diff --git a/modules/python/test/test_houghcircles.py b/modules/python/test/test_houghcircles.py
index 90cd184139..2cfc6c9d68 100644
--- a/modules/python/test/test_houghcircles.py
+++ b/modules/python/test/test_houghcircles.py
@@ -80,5 +80,52 @@ class houghcircles_test(NewOpenCVTests):
         self.assertLess(float(len(circles) - matches_counter) / len(circles), .75)
 
 
+    def test_houghcircles_alt(self):
+
+        fn = "samples/data/board.jpg"
+
+        src = self.get_sample(fn, 1)
+        img = cv.cvtColor(src, cv.COLOR_BGR2GRAY)
+        img = cv.medianBlur(img, 5)
+
+        circles = cv.HoughCircles(img, cv.HOUGH_GRADIENT_ALT, 1, 10, np.array([]), 300, 0.9, 1, 30)
+
+        self.assertEqual(circles.shape, (1, 18, 3))
+
+        circles = circles[0]
+
+        testCircles = [[38, 181, 17.6],
+        [99.7, 166, 13.12],
+        [142.7, 160, 13.52],
+        [223.6, 110, 8.62],
+        [79.1, 206.7, 8.62],
+        [47.5, 351.6, 11.64],
+        [189.5, 354.4, 11.64],
+        [189.8, 298.9, 10.64],
+        [189.5, 252.4, 14.62],
+        [252.5, 393.4, 15.62],
+        [602.9, 467.5, 11.42],
+        [222, 210.4, 9.12],
+        [263.1, 216.7, 9.12],
+        [359.8, 222.6, 9.12],
+        [518.9, 120.9, 9.12],
+        [413.8, 113.4, 9.12],
+        [489, 127.2, 9.12],
+        [448.4, 121.3, 9.12],
+        [384.6, 128.9, 8.62]]
+
+        matches_counter = 0
+
+        for i in range(len(testCircles)):
+            for j in range(len(circles)):
+
+                tstCircle = circleApproximation(testCircles[i])
+                circle = circleApproximation(circles[j])
+                if convContoursIntersectiponRate(tstCircle, circle) > 0.6:
+                    matches_counter += 1
+
+        self.assertGreater(float(matches_counter) / len(testCircles), .5)
+        self.assertLess(float(len(circles) - matches_counter) / len(circles), .75)
+
 if __name__ == '__main__':
     NewOpenCVTests.bootstrap()