apply transform to shape on render

Author: tocsoft

src/ImageSharp.Drawing/Processing/Processors/Drawing/DrawPathProcessor.cs

@@ -45,7 +45,7 @@ public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>(Configuratio
             where TPixel : unmanaged, IPixel<TPixel>
         {
             // offset drawlines to align drawing outlines to pixel centers
-            var shape = this.Shape.Translate(0.5f, 0.5f);
+            var shape = this.Shape.Translate(0.5f, 0.5f).Transform(this.Options.ShapeOptions.Transform);
             return new FillRegionProcessor(this.Options, this.Pen.StrokeFill, new ShapePath(shape, this.Pen)).CreatePixelSpecificProcessor(configuration, source, sourceRectangle);
         }
     }

src/ImageSharp.Drawing/Processing/Processors/Drawing/FillPathProcessor.cs

@@ -45,7 +45,9 @@ public FillPathProcessor(ShapeGraphicsOptions options, IBrush brush, IPath shape
         public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>(Configuration configuration, Image<TPixel> source, Rectangle sourceRectangle)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            if (this.Shape is RectangularPolygon rectPoly)
+            var shape = this.Shape.Transform(this.Options.ShapeOptions.Transform);
+
+            if (shape is RectangularPolygon rectPoly)
             {
                 var rectF = new RectangleF(rectPoly.Location, rectPoly.Size);
                 var rect = (Rectangle)rectF;
@@ -58,7 +60,7 @@ public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>(Configuratio
                 }
             }
 
-            return new FillRegionProcessor(this.Options, this.Brush, new ShapeRegion(this.Shape)).CreatePixelSpecificProcessor(configuration, source, sourceRectangle);
+            return new FillRegionProcessor(this.Options, this.Brush, new ShapeRegion(shape)).CreatePixelSpecificProcessor(configuration, source, sourceRectangle);
         }
     }
 }

src/ImageSharp.Drawing/Processing/ShapeOptions.cs

@@ -1,6 +1,7 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System.Numerics;
 using SixLabors.ImageSharp.Drawing.Shapes;
 
 namespace SixLabors.ImageSharp.Drawing.Processing
@@ -28,6 +29,11 @@ private ShapeOptions(ShapeOptions source)
         /// </summary>
         public IntersectionRule IntersectionRule { get; set; } = IntersectionRule.OddEven;
 
+        /// <summary>
+        /// Gets or sets the transform to apply to the shape during rendering.
+        /// </summary>
+        public Matrix3x2 Transform { get; set; } = Matrix3x2.Identity;
+
         /// <inheritdoc/>
         public ShapeOptions DeepClone() => new ShapeOptions(this);
     }

tests/ImageSharp.Drawing.Tests/Drawing/DrawPolygonTests.cs

@@ -36,5 +36,20 @@ public void DrawPolygon<TPixel>(TestImageProvider<TPixel> provider, string color
                 outputDetails,
                 appendSourceFileOrDescription: false);
         }
+
+        [Theory]
+        [WithBasicTestPatternImages(250, 350, PixelTypes.Rgba32)]
+        public void DrawPolygon_Transformed<TPixel>(TestImageProvider<TPixel> provider)
+           where TPixel : unmanaged, IPixel<TPixel>
+        {
+            PointF[] simplePath =
+                {
+                    new Vector2(10, 10), new Vector2(200, 150), new Vector2(50, 300)
+                };
+
+            provider.RunValidatingProcessorTest(
+                c => c.SetShapeOptions(x => x.Transform = Matrix3x2.CreateSkew(GeometryUtilities.DegreeToRadian(-15), 0, new Vector2(200, 200)))
+                .DrawPolygon(Color.White, 2.5f, simplePath));
+        }
     }
 }

tests/ImageSharp.Drawing.Tests/Drawing/FillPolygonTests.cs

@@ -67,6 +67,21 @@ public void FillPolygon_Solid<TPixel>(TestImageProvider<TPixel> provider, string
                 appendSourceFileOrDescription: false);
         }
 
+        [Theory]
+        [WithBasicTestPatternImages(250, 350, PixelTypes.Rgba32)]
+        public void FillPolygon_Solid_Transformed<TPixel>(TestImageProvider<TPixel> provider)
+           where TPixel : unmanaged, IPixel<TPixel>
+        {
+            PointF[] simplePath =
+                {
+                    new Vector2(10, 10), new Vector2(200, 150), new Vector2(50, 300)
+                };
+
+            provider.RunValidatingProcessorTest(
+                c => c.SetShapeOptions(x => x.Transform = Matrix3x2.CreateSkew(GeometryUtilities.DegreeToRadian(-15), 0, new Vector2(200, 200)))
+                .FillPolygon(Color.White, simplePath));
+        }
+
         public static TheoryData<bool, IntersectionRule> FillPolygon_Complex_Data { get; } =
             new TheoryData<bool, IntersectionRule>()
             {