Added support for mask-type style in mask attribute.

src/Svg.Model/MaskType.cs

@@ -0,0 +1,24 @@
+namespace Svg.Model;
+
+/// <summary>
+///     Specifies how the pixel content of a mask element is used when applied.
+///     Corresponds to the CSS <c>mask-type</c> property on the mask element.
+/// </summary>
+/// <remarks>
+///     SVG spec: https://www.w3.org/TR/css-masking-1/#the-mask-type
+/// </remarks>
+public enum MaskType
+{
+    /// <summary>
+    ///     Default. The luminance values of the mask content determine the mask.
+    ///     White (high luminance) = fully visible, Black (zero luminance) = fully masked.
+    /// </summary>
+    Luminance,
+
+    /// <summary>
+    ///     The alpha channel of the mask content determines the mask.
+    ///     Opaque pixels = fully visible, transparent pixels = fully masked.
+    ///     This is what <c>style="mask-type:alpha"</c> sets.
+    /// </summary>
+    Alpha
+}

src/Svg.SceneGraph/SvgSceneResource.cs

@@ -146,8 +146,9 @@ internal void AddDependentCompilationRoot(string compilationRootKey)
             }
 
             sceneDocument.ResolveRuntimePayloadTree(maskNode);
+            var maskType = GetMaskType(svgMask);
 
-            var payload = new SvgSceneMaskPayload(maskNode, CreateMaskPaint(), CreateMaskDstInPaint());
+            var payload = new SvgSceneMaskPayload(maskNode, CreateMaskPaint(), CreateMaskDstInPaint(maskType));
             _maskPayloads.Add(cacheKey, payload);
             return payload;
         }
@@ -231,15 +232,15 @@ private static SKPaint CreateMaskPaint()
         };
     }
 
-    private static SKPaint CreateMaskDstInPaint()
+    private static SKPaint CreateMaskDstInPaint(MaskType maskType)
     {
         return new SKPaint
         {
             IsAntialias = true,
             Style = SKPaintStyle.StrokeAndFill,
             BlendMode = SKBlendMode.DstIn,
             Color = FilterEffectsService.s_transparentBlack,
-            ColorFilter = SKColorFilter.CreateLumaColor()
+            ColorFilter = maskType == MaskType.Alpha ? null : SKColorFilter.CreateLumaColor()
         };
     }
 
@@ -261,10 +262,27 @@ private static SvgSceneMaskPayload CreateEmptyMaskPayload(SvgMask svgMask)
             TotalTransform = SKMatrix.Identity,
             TransformedBounds = SKRect.Empty
         };
+
+        var maskType = GetMaskType(svgMask);
 
         SvgSceneCompiler.AssignRetainedVisualState(maskNode, svgMask);
         SvgSceneCompiler.AssignRetainedResourceKeys(maskNode, svgMask);
-        return new SvgSceneMaskPayload(maskNode, CreateMaskPaint(), CreateMaskDstInPaint());
+        return new SvgSceneMaskPayload(maskNode, CreateMaskPaint(), CreateMaskDstInPaint(maskType));
+    }
+
+    private static MaskType GetMaskType(SvgMask mask)
+    {
+        var maskType = MaskType.Luminance;
+
+        if (mask.TryGetAttribute("mask-type", out var maskTypeStr)
+            && !string.IsNullOrWhiteSpace(maskTypeStr))
+        {
+            return string.Equals(maskTypeStr.Trim(), "alpha", StringComparison.OrdinalIgnoreCase)
+                ? MaskType.Alpha
+                : MaskType.Luminance;
+        }
+
+        return maskType;
     }
 
     private sealed class ReadOnlySetView<T> : IReadOnlyCollection<T> where T : notnull