Restored check that it is the end of edges being connected

Tests/test_imagedraw.py

@@ -1694,6 +1694,14 @@ def test_polygon2() -> None:
     assert_image_similar_tofile(im, expected, 1)
 
 
+def test_polygon3() -> None:
+    im = Image.new("RGB", (W, H))
+    draw = ImageDraw.Draw(im)
+    draw.polygon([(10, 10), (10, 90), (90, 90), (90, 10), (80, 10), (60, 50), (50, 10), (40, 50), (20, 80), (20, 10)], "red")
+    expected = "Tests/images/imagedraw_polygon3_RGB.png"
+    assert_image_equal_tofile(im, expected)
+
+
 @pytest.mark.parametrize("xy", ((1, 1, 0, 1), (1, 1, 1, 0)))
 def test_incorrectly_ordered_coordinates(xy: tuple[int, int, int, int]) -> None:
     im = Image.new("RGB", (W, H))

src/libImaging/Draw.c

@@ -511,8 +511,10 @@ polygon_generic(
                             continue;
                         }
                         // Check if the two edges join to make a corner
-                        if (xx[j - 1] ==
-                            (ymin - other_edge->y0) * other_edge->dx + other_edge->x0) {
+                        if (((ymin == current->ymin && ymin == other_edge->ymin) ||
+                             (ymin == current->ymax && ymin == other_edge->ymax)) &&
+                            xx[j - 1] == (ymin - other_edge->y0) * other_edge->dx +
+                                             other_edge->x0) {
                             // Determine points from the edges on the next row
                             // Or if this is the last row, check the previous row
                             int offset = ymin == ymax ? -1 : 1;