From 93a882d2e2b7acd9f00555851b5f5e7acc59e5c9 Mon Sep 17 00:00:00 2001
From: inayd <121136285+inayd@users.noreply.github.com>
Date: Tue, 1 Oct 2024 21:17:42 +0200
Subject: [PATCH] Fix fillPoly drawing over boundaries

---
 modules/imgproc/src/drawing.cpp       | 27 ++++-------
 modules/imgproc/test/test_drawing.cpp | 69 +++++++++++++++++++++++++++
 2 files changed, 78 insertions(+), 18 deletions(-)

diff --git a/modules/imgproc/src/drawing.cpp b/modules/imgproc/src/drawing.cpp
index 394a6d6059..c6efd4f21a 100644
--- a/modules/imgproc/src/drawing.cpp
+++ b/modules/imgproc/src/drawing.cpp
@@ -64,7 +64,7 @@ CollectPolyEdges( Mat& img, const Point2l* v, int npts,
                   int shift, Point offset=Point() );
 
 static void
-FillEdgeCollection( Mat& img, std::vector<PolyEdge>& edges, const void* color, int line_type);
+FillEdgeCollection( Mat& img, std::vector<PolyEdge>& edges, const void* color );
 
 static void
 PolyLine( Mat& img, const Point2l* v, int npts, bool closed,
@@ -1051,7 +1051,7 @@ EllipseEx( Mat& img, Point2l center, Size2l axes,
         v.push_back(center);
         std::vector<PolyEdge> edges;
         CollectPolyEdges( img,  &v[0], (int)v.size(), edges, color, line_type, XY_SHIFT );
-        FillEdgeCollection( img, edges, color, line_type );
+        FillEdgeCollection( img, edges, color );
     }
 }
 
@@ -1299,15 +1299,11 @@ CollectPolyEdges( Mat& img, const Point2l* v, int count, std::vector<PolyEdge>&
                 if (t0.y != t1.y)
                 {
                     pt0c.y = t0.y; pt1c.y = t1.y;
-                    pt0c.x = (int64)(t0.x) << XY_SHIFT;
-                    pt1c.x = (int64)(t1.x) << XY_SHIFT;
                 }
             }
-            else
-            {
-                pt0c.x += XY_ONE >> 1;
-                pt1c.x += XY_ONE >> 1;
-            }
+
+            pt0c.x = (int64)(t0.x) << XY_SHIFT;
+            pt1c.x = (int64)(t1.x) << XY_SHIFT;
         }
         else
         {
@@ -1349,7 +1345,7 @@ struct CmpEdges
 /**************** helper macros and functions for sequence/contour processing ***********/
 
 static void
-FillEdgeCollection( Mat& img, std::vector<PolyEdge>& edges, const void* color, int line_type)
+FillEdgeCollection( Mat& img, std::vector<PolyEdge>& edges, const void* color )
 {
     PolyEdge tmp;
     int i, y, total = (int)edges.size();
@@ -1358,12 +1354,7 @@ FillEdgeCollection( Mat& img, std::vector<PolyEdge>& edges, const void* color, i
     int y_max = INT_MIN, y_min = INT_MAX;
     int64 x_max = 0xFFFFFFFFFFFFFFFF, x_min = 0x7FFFFFFFFFFFFFFF;
     int pix_size = (int)img.elemSize();
-    int delta;
-
-    if (line_type < cv::LINE_AA)
-        delta = 0;
-    else
-        delta = XY_ONE - 1;
+    int delta = XY_ONE - 1;
 
     if( total < 2 )
         return;
@@ -2051,7 +2042,7 @@ void fillPoly( InputOutputArray _img, const Point** pts, const int* npts, int nc
         }
     }
 
-    FillEdgeCollection(img, edges, buf, line_type);
+    FillEdgeCollection(img, edges, buf);
 }
 
 void polylines( InputOutputArray _img, const Point* const* pts, const int* npts, int ncontours, bool isClosed,
@@ -2690,7 +2681,7 @@ cvDrawContours( void* _img, CvSeq* contour,
     }
 
     if( thickness < 0 )
-        cv::FillEdgeCollection( img, edges, ext_buf, line_type);
+        cv::FillEdgeCollection( img, edges, ext_buf );
 
     if( h_next && contour0 )
         contour0->h_next = h_next;
diff --git a/modules/imgproc/test/test_drawing.cpp b/modules/imgproc/test/test_drawing.cpp
index a6b125bcd1..fb7aeb0382 100644
--- a/modules/imgproc/test/test_drawing.cpp
+++ b/modules/imgproc/test/test_drawing.cpp
@@ -680,6 +680,75 @@ TEST(Drawing, fillpoly_circle)
     EXPECT_LT(diff_fp3, 1.);
 }
 
+TEST(Drawing, fillpoly_contours)
+{
+    const int imgSize = 50;
+    const int type = CV_8UC1;
+    const int shift = 0;
+    const Scalar cl = Scalar::all(255);
+    const cv::LineTypes lineType = LINE_8;
+
+    // check that contours of fillPoly and polylines match
+    {
+        cv::Mat img(imgSize, imgSize, type);
+        img = 0;
+        std::vector<std::vector<cv::Point>> polygonPoints{
+            { {44, 27}, {7, 37}, {7, 19}, {38, 19} }
+        };
+        cv::fillPoly(img, polygonPoints, cl, lineType, shift);
+        cv::polylines(img, polygonPoints, true, 0, 1, lineType, shift);
+
+        {
+            cv::Mat labelImage(img.size(), CV_32S);
+            int labels = cv::connectedComponents(img, labelImage, 4);
+            EXPECT_EQ(2, labels) << "filling went over the border";
+        }
+    }
+
+    // check that line generated with fillPoly and polylines match
+    {
+        cv::Mat img1(imgSize, imgSize, type), img2(imgSize, imgSize, type);
+        img1 = 0;
+        img2 = 0;
+        std::vector<std::vector<cv::Point>> polygonPoints{
+            { {44, 27}, {38, 19} }
+        };
+        cv::fillPoly(img1, polygonPoints, cl, lineType, shift);
+        cv::polylines(img2, polygonPoints, true, cl, 1, lineType, shift);
+        EXPECT_MAT_N_DIFF(img1, img2, 0);
+    }
+}
+
+TEST(Drawing, fillpoly_match_lines)
+{
+    const int imgSize = 49;
+    const int type = CV_8UC1;
+    const int shift = 0;
+    const Scalar cl = Scalar::all(255);
+    const cv::LineTypes lineType = LINE_8;
+    cv::Mat img1(imgSize, imgSize, type), img2(imgSize, imgSize, type);
+    for (int x1 = 0; x1 < imgSize; x1 += imgSize / 2)
+    {
+        for (int y1 = 0; y1 < imgSize; y1 += imgSize / 2)
+        {
+            for (int x2 = 0; x2 < imgSize; x2++)
+            {
+                for (int y2 = 0; y2 < imgSize; y2++)
+                {
+                    img1 = 0;
+                    img2 = 0;
+                    std::vector<std::vector<cv::Point>> polygonPoints{
+                        { {x1, y1}, {x2, y2} }
+                    };
+                    cv::fillPoly(img1, polygonPoints, cl, lineType, shift);
+                    cv::polylines(img2, polygonPoints, true, cl, 1, lineType, shift);
+                    EXPECT_MAT_N_DIFF(img1, img2, 0);
+                }
+            }
+        }
+    }
+}
+
 TEST(Drawing, fillpoly_fully)
 {
     unsigned imageWidth = 256;