Migrate drawing transforms to Matrix4x4

Author: JimBobSquarePants

samples/DrawShapesWithImageSharp/Program.cs

@@ -267,7 +267,7 @@ public static void SaveImageWithPath(this IPathCollection collection, IPath shap
         {
             // Fill the canvas background and draw our shape.
             canvas.Fill(Brushes.Solid(Color.DarkBlue));
-            canvas.Fill(shape, Brushes.Solid(Color.White.WithAlpha(.25F)));
+            canvas.Fill(Brushes.Solid(Color.White.WithAlpha(.25F)), shape);
 
             // Draw our path collection.
             canvas.Fill(Brushes.Solid(Color.HotPink), collection);

samples/WebGPUWindowDemo/Program.cs

@@ -304,7 +304,7 @@ private static void OnRender(double deltaTime)
             {
                 ref Ball ball = ref balls[i];
                 EllipsePolygon ellipse = new(ball.X, ball.Y, ball.Radius);
-                canvas.Fill(ellipse, Brushes.Solid(ball.Color));
+                canvas.Fill(Brushes.Solid(ball.Color), ellipse);
             }
 
             // Flush submits all queued draw operations to the GPU compositor and
@@ -367,7 +367,7 @@ private static void DrawScrollingText(DrawingCanvas<Bgra32> canvas, int w, int h
                 continue;
             }
 
-            canvas.Fill(path.Transform(translation), textBrush);
+            canvas.Fill(textBrush, path.Transform(new Matrix4x4(translation)));
         }
     }
 

src/ImageSharp.Drawing.WebGPU/Shaders/CompositeComputeShader.cs

@@ -275,7 +275,7 @@ fn elliptic_gradient_t(x: f32, y: f32, cmd: Params) -> f32 {
 
             if rx_sq < 1e-20 { return 0.0; }
             if ry_sq < 1e-20 { return 0.0; }
-            return rotated_x * rotated_x / rx_sq + rotated_y * rotated_y / ry_sq;
+            return sqrt(rotated_x * rotated_x / rx_sq + rotated_y * rotated_y / ry_sq);
         }
 
         // Sweep (angular) gradient. Computes radians and sweep from raw degrees.

src/ImageSharp.Drawing/ArcLineSegment.cs

@@ -93,7 +93,7 @@ public ArcLineSegment(PointF center, SizeF radius, float rotation, float startAn
     /// </summary>
     /// <param name="matrix">The transformation matrix.</param>
     /// <returns>An <see cref="ArcLineSegment"/> with the matrix applied to it.</returns>
-    public ILineSegment Transform(Matrix3x2 matrix)
+    public ILineSegment Transform(Matrix4x4 matrix)
     {
         if (matrix.IsIdentity)
         {
@@ -110,7 +110,7 @@ public ILineSegment Transform(Matrix3x2 matrix)
     }
 
     /// <inheritdoc/>
-    ILineSegment ILineSegment.Transform(Matrix3x2 matrix) => this.Transform(matrix);
+    ILineSegment ILineSegment.Transform(Matrix4x4 matrix) => this.Transform(matrix);
 
     private static PointF[] EllipticArcFromEndParams(
         PointF from,

src/ImageSharp.Drawing/ComplexPolygon.cs

@@ -67,7 +67,7 @@ public ComplexPolygon(params IPath[] paths)
     public RectangleF Bounds => this.bounds ??= this.CalcBounds();
 
     /// <inheritdoc/>
-    public IPath Transform(Matrix3x2 matrix)
+    public IPath Transform(Matrix4x4 matrix)
     {
         if (matrix.IsIdentity)
         {

src/ImageSharp.Drawing/CubicBezierLineSegment.cs

@@ -81,7 +81,7 @@ public CubicBezierLineSegment(PointF start, PointF controlPoint1, PointF control
     /// </summary>
     /// <param name="matrix">The matrix.</param>
     /// <returns>A line segment with the matrix applied to it.</returns>
-    public CubicBezierLineSegment Transform(Matrix3x2 matrix)
+    public CubicBezierLineSegment Transform(Matrix4x4 matrix)
     {
         if (matrix.IsIdentity)
         {
@@ -100,7 +100,7 @@ public CubicBezierLineSegment Transform(Matrix3x2 matrix)
     }
 
     /// <inheritdoc/>
-    ILineSegment ILineSegment.Transform(Matrix3x2 matrix) => this.Transform(matrix);
+    ILineSegment ILineSegment.Transform(Matrix4x4 matrix) => this.Transform(matrix);
 
     private static PointF[] GetDrawingPoints(PointF[] controlPoints)
     {

src/ImageSharp.Drawing/EllipsePolygon.cs

@@ -59,7 +59,7 @@ public EllipsePolygon(float x, float y, float radius)
     }
 
     /// <inheritdoc/>
-    public override IPath Transform(Matrix3x2 matrix)
+    public override IPath Transform(Matrix4x4 matrix)
     {
         if (matrix.IsIdentity)
         {

src/ImageSharp.Drawing/EmptyPath.cs

@@ -35,5 +35,5 @@ public sealed class EmptyPath : IPath
     public IEnumerable<ISimplePath> Flatten() => [];
 
     /// <inheritdoc />
-    public IPath Transform(Matrix3x2 matrix) => this;
+    public IPath Transform(Matrix4x4 matrix) => this;
 }

src/ImageSharp.Drawing/Helpers/MatrixUtilities.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Numerics;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp.Drawing.Helpers;
+
+/// <summary>
+/// Provides helper methods for extracting properties from transformation matrices.
+/// </summary>
+internal static class MatrixUtilities
+{
+    /// <summary>
+    /// Extracts the average 2D scale factor from a <see cref="Matrix4x4"/>.
+    /// This is the mean of the X and Y axis scale magnitudes, suitable for
+    /// uniformly scaling radii under non-uniform or projective transforms.
+    /// </summary>
+    /// <param name="matrix">The transformation matrix.</param>
+    /// <returns>The average scale factor.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static float GetAverageScale(in Matrix4x4 matrix)
+    {
+        float sx = MathF.Sqrt((matrix.M11 * matrix.M11) + (matrix.M12 * matrix.M12));
+        float sy = MathF.Sqrt((matrix.M21 * matrix.M21) + (matrix.M22 * matrix.M22));
+        return (sx + sy) * 0.5f;
+    }
+}

src/ImageSharp.Drawing/ILineSegment.cs

@@ -29,5 +29,5 @@ public interface ILineSegment
     /// </summary>
     /// <param name="matrix">The matrix.</param>
     /// <returns>A line segment with the matrix applied to it.</returns>
-    ILineSegment Transform(Matrix3x2 matrix);
+    ILineSegment Transform(Matrix4x4 matrix);
 }