[Skia] Fix RadialGradientBrush for non center origin

AvaloniaUI · Jan 8, 2025 · 29ee228 · 29ee228
1 parent 0dd628f
commit 29ee228
Showing 1 changed file with 10 additions and 55 deletions.
diff --git a/src/Skia/Avalonia.Skia/DrawingContextImpl.cs b/src/Skia/Avalonia.Skia/DrawingContextImpl.cs
@@ -917,13 +917,16 @@ private static void ConfigureGradientBrush(ref PaintWrapper paintWrapper, Rect t
                 case IRadialGradientBrush radialGradient:
                 {
                     var centerPoint = radialGradient.Center.ToPixels(targetRect);
-                    var center = centerPoint.ToSKPoint();
 
                     var radiusX = (radialGradient.RadiusX.ToValue(targetRect.Width));
                     var radiusY = (radialGradient.RadiusY.ToValue(targetRect.Height));
 
                     var originPoint = radialGradient.GradientOrigin.ToPixels(targetRect);
-
+
+                    centerPoint += new Point(originPoint.X - targetRect.Width / 2, originPoint.Y - targetRect.Height / 2);
+
+                    var center = centerPoint.ToSKPoint();
+
                     Matrix? transform = null;
 
                     if (radiusX != radiusY)
@@ -940,61 +943,13 @@ private static void ConfigureGradientBrush(ref PaintWrapper paintWrapper, Rect t
                         var brushTransform = (-offset) * radialGradient.Transform.Value * (offset);
                         transform = transform.HasValue ? transform * brushTransform : brushTransform;
                     }
-
-                    if (originPoint.Equals(centerPoint))
-                    {
-                        // when the origin is the same as the center the Skia RadialGradient acts the same as D2D
-                        using (var shader =
-                               transform.HasValue
-                                   ? SKShader.CreateRadialGradient(center, (float)radiusX, stopColors, stopOffsets, tileMode,
-                                       transform.Value.ToSKMatrix())
-                                   : SKShader.CreateRadialGradient(center, (float)radiusX, stopColors, stopOffsets, tileMode)
-                              )
-                        {
-                            paintWrapper.Paint.Shader = shader;
-                        }
-                    }
-                    else
-                    {
-                        // when the origin is different to the center use a two point ConicalGradient to match the behaviour of D2D
 
-                        if (radiusX != radiusY)
-                            // Adjust the origin point for radiusX/Y transformation by reversing it
-                            originPoint = originPoint.WithY(
-                                (originPoint.Y - centerPoint.Y) * radiusX / radiusY + centerPoint.Y);
-
-                        var origin = originPoint.ToSKPoint();
-
-                        // reverse the order of the stops to match D2D
-                        var reversedColors = new SKColor[stopColors.Length];
-                        Array.Copy(stopColors, reversedColors, stopColors.Length);
-                        Array.Reverse(reversedColors);
-
-                        // and then reverse the reference point of the stops
-                        var reversedStops = new float[stopOffsets.Length];
-                        for (var i = 0; i < stopOffsets.Length; i++)
-                        {
-                            reversedStops[i] = stopOffsets[i];
-                            if (reversedStops[i] > 0 && reversedStops[i] < 1)
-                            {
-                                reversedStops[i] = Math.Abs(1 - stopOffsets[i]);
-                            }
-                        }
-
-                        // compose with a background colour of the final stop to match D2D's behaviour of filling with the final color
-                        using (var shader = SKShader.CreateCompose(
-                                   SKShader.CreateColor(reversedColors[0]),
-                                   transform.HasValue
-                                       ? SKShader.CreateTwoPointConicalGradient(center, (float)radiusX, origin, 0,
-                                           reversedColors, reversedStops, tileMode, transform.Value.ToSKMatrix())
-                                       : SKShader.CreateTwoPointConicalGradient(center, (float)radiusX, origin, 0,
-                                           reversedColors, reversedStops, tileMode)
-
-                               )
-                              )
-                        {
+                    using (var shader = transform.HasValue
+                                       ? SKShader.CreateRadialGradient(center, (float)radiusX, stopColors, stopOffsets, tileMode,
+                                           transform.Value.ToSKMatrix())
+                                       : SKShader.CreateRadialGradient(center, (float)radiusX, stopColors, stopOffsets, tileMode))
+                    {
                             paintWrapper.Paint.Shader = shader;
-                        }
                     }
 
                     break;