Merge pull request #119 from SixLabors/js/fix-108

Fix IndexOutOfRangeException when drawing lines outside of image

Author: JimBobSquarePants

src/ImageSharp.Drawing/Shapes/Rasterization/PolygonScanner.cs

@@ -151,12 +151,12 @@ private void SkipEdgesBeforeMinY()
 
                 if (y0 < y1)
                 {
-                    this.SubPixelY = y0;
+                    this.SubPixelY = y1;
                     i0++;
                 }
                 else
                 {
-                    this.SubPixelY = y1;
+                    this.SubPixelY = y0;
                     i1++;
                 }
             }

tests/ImageSharp.Drawing.Tests/Issues/Issue_28.cs renamed to tests/ImageSharp.Drawing.Tests/Issues/Issue_28_108.cs

@@ -10,72 +10,87 @@
 
 namespace SixLabors.ImageSharp.Drawing.Tests.Issues
 {
-    public class Issue_28
+    public class Issue_28_108
     {
         private Rgba32 red = Color.Red.ToRgba32();
 
-        [Fact]
-        public void DrawingLineAtTopShouldDisplay()
+        [Theory]
+        [InlineData(1F)]
+        [InlineData(1.5F)]
+        [InlineData(2F)]
+        [InlineData(3F)]
+        public void DrawingLineAtTopShouldDisplay(float stroke)
         {
             using var image = new Image<Rgba32>(Configuration.Default, 100, 100, Color.Black);
             image.Mutate(x => x
                     .SetGraphicsOptions(g => g.Antialias = false)
                     .DrawLines(
                         this.red,
-                        1f,
+                        stroke,
                         new PointF(0, 0),
                         new PointF(100, 0)));
 
             IEnumerable<(int x, int y)> locations = Enumerable.Range(0, 100).Select(i => (x: i, y: 0));
             Assert.All(locations, l => Assert.Equal(this.red, image[l.x, l.y]));
         }
 
-        [Fact]
-        public void DrawingLineAtBottomShouldDisplay()
+        [Theory]
+        [InlineData(1F)]
+        [InlineData(1.5F)]
+        [InlineData(2F)]
+        [InlineData(3F)]
+        public void DrawingLineAtBottomShouldDisplay(float stroke)
         {
             using var image = new Image<Rgba32>(Configuration.Default, 100, 100, Color.Black);
             image.Mutate(x => x
                     .SetGraphicsOptions(g => g.Antialias = false)
                     .DrawLines(
                         this.red,
-                        1f,
+                        stroke,
                         new PointF(0, 99),
                         new PointF(100, 99)));
 
             IEnumerable<(int x, int y)> locations = Enumerable.Range(0, 100).Select(i => (x: i, y: 99));
             Assert.All(locations, l => Assert.Equal(this.red, image[l.x, l.y]));
         }
 
-        [Fact]
-        public void DrawingLineAtLeftShouldDisplay()
+        [Theory]
+        [InlineData(1F)]
+        [InlineData(1.5F)]
+        [InlineData(2F)]
+        [InlineData(3F)]
+        public void DrawingLineAtLeftShouldDisplay(float stroke)
         {
             using var image = new Image<Rgba32>(Configuration.Default, 100, 100, Color.Black);
             image.Mutate(x => x
                     .SetGraphicsOptions(g => g.Antialias = false)
                     .DrawLines(
                         this.red,
-                        1f,
+                        stroke,
                         new PointF(0, 0),
                         new PointF(0, 99)));
 
             IEnumerable<(int x, int y)> locations = Enumerable.Range(0, 100).Select(i => (x: 0, y: i));
             Assert.All(locations, l => Assert.Equal(this.red, image[l.x, l.y]));
         }
 
-        [Fact]
-        public void DrawingLineAtRightShouldDisplay()
+        [Theory]
+        [InlineData(1F)]
+        [InlineData(1.5F)]
+        [InlineData(2F)]
+        [InlineData(3F)]
+        public void DrawingLineAtRightShouldDisplay(float stroke)
         {
             using var image = new Image<Rgba32>(Configuration.Default, 100, 100, Color.Black);
             image.Mutate(x => x
                     .SetGraphicsOptions(g => g.Antialias = false)
                     .DrawLines(
                         this.red,
-                        1f,
+                        stroke,
                         new PointF(99, 0),
                         new PointF(99, 99)));
 
             IEnumerable<(int x, int y)> locations = Enumerable.Range(0, 100).Select(i => (x: 99, y: i));
-
             Assert.All(locations, l => Assert.Equal(this.red, image[l.x, l.y]));
         }
     }

tests/ImageSharp.Drawing.Tests/Shapes/Scan/PolygonScannerTests.cs

@@ -426,6 +426,25 @@ public void NegativeOrientation01(IntersectionRule intersectionRule)
             this.TestScan(poly, 0, 2, 2, expected, intersectionRule);
         }
 
+        [Fact]
+        public void OutOfBounds()
+        {
+            IPath poly = PolygonFactory.CreatePolygon((1, -5), (5, -5), (5, -3), (10, -1), (10, 2), (12, 4), (1, 4));
+
+            FuzzyFloat[][] exected =
+            {
+                new FuzzyFloat[] { 1, 10 },
+                new FuzzyFloat[] { 1, 10 },
+                new FuzzyFloat[] { 1, 10 },
+                new FuzzyFloat[] { 1, 10 },
+                new FuzzyFloat[] { 1, 10 },
+                new FuzzyFloat[] { 1, 10.5 },
+                new FuzzyFloat[] { 1, 11 },
+            };
+
+            this.TestScan(poly, 0, 3, 2, exected);
+        }
+
         private static (float y, FuzzyFloat[] x) Empty(float y) => (y, new FuzzyFloat[0]);
 
         private static FuzzyFloat F(float x, float eps) => new FuzzyFloat(x, eps);