Expose ImageBrush source region constructor.

src/ImageSharp.Drawing/Processing/ImageBrush.cs

@@ -24,7 +24,7 @@ public class ImageBrush : Brush
     /// <summary>
     /// Initializes a new instance of the <see cref="ImageBrush"/> class.
     /// </summary>
-    /// <param name="image">The image.</param>
+    /// <param name="image">The source image to draw.</param>
     public ImageBrush(Image image)
         : this(image, image.Bounds)
     {
@@ -33,15 +33,12 @@ public ImageBrush(Image image)
     /// <summary>
     /// Initializes a new instance of the <see cref="ImageBrush"/> class.
     /// </summary>
-    /// <param name="image">The image.</param>
-    /// <param name="region">
-    /// The region of interest.
-    /// This overrides any region used to initialize the brush applicator.
-    /// </param>
-    internal ImageBrush(Image image, RectangleF region)
+    /// <param name="image">The source image.</param>
+    /// <param name="region">The region of interest within the source image to draw.</param>
+    public ImageBrush(Image image, RectangleF region)
     {
         this.image = image;
-        this.region = region;
+        this.region = RectangleF.Intersect(image.Bounds, region);
     }
 
     /// <inheritdoc />

tests/ImageSharp.Drawing.Tests/Drawing/FillImageBrushTests.cs

@@ -14,10 +14,10 @@ public class FillImageBrushTests
     [Fact]
     public void DoesNotDisposeImage()
     {
-        using (var src = new Image<Rgba32>(5, 5))
+        using (Image<Rgba32> src = new(5, 5))
         {
-            var brush = new ImageBrush(src);
-            using (var dest = new Image<Rgba32>(10, 10))
+            ImageBrush brush = new(src);
+            using (Image<Rgba32> dest = new(10, 10))
             {
                 dest.Mutate(c => c.Fill(brush, new Rectangle(0, 0, 10, 10)));
                 dest.Mutate(c => c.Fill(brush, new Rectangle(0, 0, 10, 10)));
@@ -36,7 +36,7 @@ public void UseBrushOfDifferentPixelType<TPixel>(TestImageProvider<TPixel> provi
                                    ? Image.Load<Bgra32>(data)
                                    : Image.Load<Rgba32>(data);
 
-        var brush = new ImageBrush(overlay);
+        ImageBrush brush = new(overlay);
         background.Mutate(c => c.Fill(brush));
 
         background.DebugSave(provider, appendSourceFileOrDescription: false);
@@ -54,7 +54,7 @@ public void CanDrawLandscapeImage<TPixel>(TestImageProvider<TPixel> provider)
 
         overlay.Mutate(c => c.Crop(new Rectangle(0, 0, 125, 90)));
 
-        var brush = new ImageBrush(overlay);
+        ImageBrush brush = new(overlay);
         background.Mutate(c => c.Fill(brush));
 
         background.DebugSave(provider, appendSourceFileOrDescription: false);
@@ -72,10 +72,61 @@ public void CanDrawPortraitImage<TPixel>(TestImageProvider<TPixel> provider)
 
         overlay.Mutate(c => c.Crop(new Rectangle(0, 0, 90, 125)));
 
-        var brush = new ImageBrush(overlay);
+        ImageBrush brush = new(overlay);
         background.Mutate(c => c.Fill(brush));
 
         background.DebugSave(provider, appendSourceFileOrDescription: false);
         background.CompareToReferenceOutput(provider, appendSourceFileOrDescription: false);
     }
+
+    [Theory]
+    [WithSolidFilledImages(1000, 1000, "White", PixelTypes.Rgba32)]
+    public void CanDrawNegativeOffsetImage<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        byte[] data = TestFile.Create(TestImages.Png.Ducky).Bytes;
+        using Image<TPixel> background = provider.GetImage();
+        using Image overlay = Image.Load<Rgba32>(data);
+
+        overlay.Mutate(c => c.Resize(100, 100));
+
+        ImageBrush halfBrush = new(overlay, new RectangleF(50, 0, 50, 100));
+        ImageBrush fullBrush = new(overlay);
+        background.Mutate(c => DrawFull(c, new Size(100, 100), fullBrush, halfBrush, background.Width, background.Height));
+
+        background.DebugSave(provider, appendSourceFileOrDescription: false);
+        background.CompareToReferenceOutput(provider, appendSourceFileOrDescription: false);
+    }
+
+    private static void DrawFull(IImageProcessingContext ctx, Size size, ImageBrush brush, ImageBrush halfBrush, int width, int height)
+    {
+        int j = 0;
+        while (j < height)
+        {
+            bool half = false;
+            int limitWidth = width;
+            int i = 0;
+            if ((j / size.Height) % 2 != 0)
+            {
+                half = true;
+            }
+
+            while (i < limitWidth)
+            {
+                if (half)
+                {
+                    ctx.Fill(halfBrush, new RectangleF(i, j, size.Width / 2f, size.Height));
+                    i += (int)(size.Width / 2f);
+                    half = false;
+                }
+                else
+                {
+                    ctx.Fill(brush, new RectangleF(new PointF(i, j), size));
+                    i += size.Width;
+                }
+            }
+
+            j += size.Height;
+        }
+    }
 }