Fix gradient brushes

Author: JimBobSquarePants

src/ImageSharp.Drawing.WebGPU/Shaders/WgslSource/Shared/transform.wgsl

@@ -46,10 +46,15 @@ fn transform_inverse(transform: Transform) -> Transform {
     let det = a * (e * i - f * h) - b * (d * i - f * g) + c * (d * h - e * g);
     let inv_det = 1.0 / det;
 
+    // The packed fields represent the matrix:
+    // [ a d g ]
+    // [ b e h ]
+    // [ c f i ]
+    // so the cofactors must be placed back into that same layout.
     return Transform(
-        inv_det * vec4(e * i - f * h, f * g - d * i, c * h - b * i, a * i - c * g),
-        inv_det * vec2(b * f - c * e, c * d - a * f),
-        inv_det * vec3(d * h - e * g, b * g - a * h, a * e - b * d)
+        inv_det * vec4(e * i - f * h, c * h - b * i, f * g - d * i, a * i - c * g),
+        inv_det * vec2(d * h - e * g, b * g - a * h),
+        inv_det * vec3(b * f - c * e, c * d - a * f, a * e - b * d)
     );
 }
 

src/ImageSharp.Drawing.WebGPU/WebGPUSceneEncoder.cs

@@ -80,7 +80,7 @@ public static bool TryEncode(
                 return true;
             }
 
-            encodedScene = SupportedSubsetSceneResolver.Resolve(encoding, targetBounds, allocator);
+            encodedScene = SupportedSubsetSceneResolver.Resolve(ref encoding, targetBounds, allocator);
             error = null;
             return true;
         }
@@ -806,7 +806,7 @@ private static class SupportedSubsetSceneResolver
         /// Resolves the mutable encoding into the final packed scene buffers.
         /// </summary>
         public static WebGPUEncodedScene Resolve(
-            SupportedSubsetSceneEncoding encoding,
+            ref SupportedSubsetSceneEncoding encoding,
             in Rectangle targetBounds,
             MemoryAllocator allocator)
         {
@@ -854,7 +854,7 @@ public static WebGPUEncodedScene Resolve(
                     encoding.InfoWordCount,
                     sceneDataOwner,
                     sceneWordCount,
-                    DetachGradientPixels(encoding),
+                    DetachGradientPixels(ref encoding),
                     encoding.Images,
                     encoding.GradientRowCount,
                     layout,
@@ -886,7 +886,7 @@ public static WebGPUEncodedScene Resolve(
         /// <summary>
         /// Detaches the gradient pixel payload when gradients were emitted for the flush.
         /// </summary>
-        private static IMemoryOwner<uint>? DetachGradientPixels(SupportedSubsetSceneEncoding encoding)
+        private static IMemoryOwner<uint>? DetachGradientPixels(ref SupportedSubsetSceneEncoding encoding)
         {
             if (encoding.GradientRowCount == 0)
             {