Add Bitmap Blending Mode API

src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs

@@ -393,7 +393,7 @@ namespace Avalonia.Headless
             {
             }
 
-            public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode = BitmapInterpolationMode.Default)
+            public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode = BitmapInterpolationMode.Default, BitmapBlendingMode bitmapBlendingMode = BitmapBlendingMode.SourceOver)
             {
                 
             }

src/Avalonia.Visuals/ApiCompatBaseline.txt

@@ -1,6 +1,9 @@
 Compat issues with assembly Avalonia.Visuals:
+InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IDrawingContextImpl.DrawBitmap(Avalonia.Utilities.IRef<Avalonia.Platform.IBitmapImpl>, System.Double, Avalonia.Rect, Avalonia.Rect, Avalonia.Visuals.Media.Imaging.BitmapInterpolationMode)' is present in the contract but not in the implementation.
+MembersMustExist : Member 'public void Avalonia.Platform.IDrawingContextImpl.DrawBitmap(Avalonia.Utilities.IRef<Avalonia.Platform.IBitmapImpl>, System.Double, Avalonia.Rect, Avalonia.Rect, Avalonia.Visuals.Media.Imaging.BitmapInterpolationMode)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IDrawingContextImpl.DrawBitmap(Avalonia.Utilities.IRef<Avalonia.Platform.IBitmapImpl>, System.Double, Avalonia.Rect, Avalonia.Rect, Avalonia.Visuals.Media.Imaging.BitmapInterpolationMode, Avalonia.Visuals.Media.Imaging.BitmapBlendingMode)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Double Avalonia.Platform.IGeometryImpl.ContourLength' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Double Avalonia.Platform.IGeometryImpl.ContourLength.get()' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Platform.IGeometryImpl.TryGetPointAndTangentAtDistance(System.Double, Avalonia.Point, Avalonia.Point)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Platform.IGeometryImpl.TryGetPointAtDistance(System.Double, Avalonia.Point)' is present in the implementation but not in the contract.
-Total Issues: 4
+Total Issues: 7

src/Avalonia.Visuals/Media/Imaging/BitmapBlendingMode.cs

@@ -0,0 +1,57 @@
+namespace Avalonia.Visuals.Media.Imaging
+{
+    /// <summary>
+    /// Controls the way the bitmaps are drawn together.
+    /// </summary>
+    public enum BitmapBlendingMode
+    {
+        /// <summary>
+        /// Source is placed over the destination.
+        /// </summary>
+        SourceOver,
+        /// <summary>
+        /// Only the source will be present.
+        /// </summary>
+        Source,
+        /// <summary>
+        /// Only the destination will be present.
+        /// </summary>
+        Destination,
+        /// <summary>
+        /// Destination is placed over the source.
+        /// </summary>
+        DestinationOver,
+        /// <summary>
+        /// The source that overlaps the destination, replaces the destination.
+        /// </summary>
+        SourceIn,
+        /// <summary>
+        /// Destination which overlaps the source, replaces the source.
+        /// </summary>
+        DestinationIn,
+        /// <summary>
+        /// Source is placed, where it falls outside of the destination.
+        /// </summary>
+        SourceOut,
+        /// <summary>
+        /// Destination is placed, where it falls outside of the source.
+        /// </summary>
+        DestinationOut,
+        /// <summary>
+        /// Source which overlaps the destination, replaces the destination.
+        /// </summary>
+        SourceAtop,
+        /// <summary>
+        /// Destination which overlaps the source replaces the source.
+        /// </summary>
+        DestinationAtop,
+        /// <summary>
+        /// The non-overlapping regions of source and destination are combined.
+        /// </summary>
+        Xor,
+        /// <summary>
+        /// Display the sum of the source image and destination image.
+        /// </summary>
+        Plus,
+    }
+}

src/Avalonia.Visuals/Platform/IDrawingContextImpl.cs

@@ -30,7 +30,8 @@ namespace Avalonia.Platform
         /// <param name="sourceRect">The rect in the image to draw.</param>
         /// <param name="destRect">The rect in the output to draw to.</param>
         /// <param name="bitmapInterpolationMode">The bitmap interpolation mode.</param>
-        void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode = BitmapInterpolationMode.Default);
+        /// <param name="bitmapBlendMode">The bitmap blending mode.</param>
+        void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode = BitmapInterpolationMode.Default, BitmapBlendingMode bitmapBlendMode = BitmapBlendingMode.SourceOver);
 
         /// <summary>
         /// Draws a bitmap image.

src/Avalonia.Visuals/Rendering/SceneGraph/DeferredDrawingContextImpl.cs

@@ -112,13 +112,13 @@ namespace Avalonia.Rendering.SceneGraph
         }
 
         /// <inheritdoc/>
-        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode)
+        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode, BitmapBlendingMode bitmapBlendingMode)
         {
             var next = NextDrawAs<ImageNode>();
 
-            if (next == null || !next.Item.Equals(Transform, source, opacity, sourceRect, destRect, bitmapInterpolationMode))
+            if (next == null || !next.Item.Equals(Transform, source, opacity, sourceRect, destRect, bitmapInterpolationMode, bitmapBlendingMode))
             {
-                Add(new ImageNode(Transform, source, opacity, sourceRect, destRect, bitmapInterpolationMode));
+                Add(new ImageNode(Transform, source, opacity, sourceRect, destRect, bitmapInterpolationMode, bitmapBlendingMode));
             }
             else
             {

src/Avalonia.Visuals/Rendering/SceneGraph/ImageNode.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <param name="sourceRect">The source rect.</param>
         /// <param name="destRect">The destination rect.</param>
         /// <param name="bitmapInterpolationMode">The bitmap interpolation mode.</param>
-        public ImageNode(Matrix transform, IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode)
+        public ImageNode(Matrix transform, IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode, BitmapBlendingMode bitmapBlendingMode)
             : base(destRect, transform)
         {
             Transform = transform;
@@ -27,6 +27,7 @@ namespace Avalonia.Rendering.SceneGraph
             SourceRect = sourceRect;
             DestRect = destRect;
             BitmapInterpolationMode = bitmapInterpolationMode;
+            BitmapBlendingMode = bitmapBlendingMode;
             SourceVersion = Source.Item.Version;
         }        
 
@@ -67,6 +68,14 @@ namespace Avalonia.Rendering.SceneGraph
         /// The scaling mode.
         /// </value>
         public BitmapInterpolationMode BitmapInterpolationMode { get; }
+        
+        /// <summary>
+        /// The bitmap blending mode.
+        /// </summary>
+        /// <value>
+        /// The blending mode.
+        /// </value>
+        public BitmapBlendingMode BitmapBlendingMode { get; }
 
         /// <summary>
         /// Determines if this draw operation equals another.
@@ -82,22 +91,23 @@ namespace Avalonia.Rendering.SceneGraph
         /// The properties of the other draw operation are passed in as arguments to prevent
         /// allocation of a not-yet-constructed draw operation object.
         /// </remarks>
-        public bool Equals(Matrix transform, IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode)
+        public bool Equals(Matrix transform, IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode, BitmapBlendingMode bitmapBlendingMode)
         {
             return transform == Transform &&
-                Equals(source.Item, Source.Item) &&
-                source.Item.Version == SourceVersion &&
-                opacity == Opacity &&
-                sourceRect == SourceRect &&
-                destRect == DestRect &&
-                bitmapInterpolationMode == BitmapInterpolationMode;
+                   Equals(source.Item, Source.Item) &&
+                   source.Item.Version == SourceVersion &&
+                   opacity == Opacity &&
+                   sourceRect == SourceRect &&
+                   destRect == DestRect &&
+                   bitmapInterpolationMode == BitmapInterpolationMode &&
+                   bitmapBlendingMode == BitmapBlendingMode;
         }
 
         /// <inheritdoc/>
         public override void Render(IDrawingContextImpl context)
         {
             context.Transform = Transform;
-            context.DrawBitmap(Source, Opacity, SourceRect, DestRect, BitmapInterpolationMode);
+            context.DrawBitmap(Source, Opacity, SourceRect, DestRect, BitmapInterpolationMode, BitmapBlendingMode);
         }
 
         /// <inheritdoc/>

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -132,7 +132,7 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode)
+        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode, BitmapBlendingMode bitmapBlendingMode)
         {
             var drawableImage = (IDrawableBitmapImpl)source.Item;
             var s = sourceRect.ToSKRect();
@@ -145,6 +145,7 @@ namespace Avalonia.Skia
                 })
             {
                 paint.FilterQuality = bitmapInterpolationMode.ToSKFilterQuality();
+                paint.BlendMode = bitmapBlendingMode.ToSKBlendMode();
 
                 drawableImage.Draw(this, s, d, paint);
             }
@@ -154,7 +155,7 @@ namespace Avalonia.Skia
         public void DrawBitmap(IRef<IBitmapImpl> source, IBrush opacityMask, Rect opacityMaskRect, Rect destRect)
         {
             PushOpacityMask(opacityMask, opacityMaskRect);
-            DrawBitmap(source, 1, new Rect(0, 0, source.Item.PixelSize.Width, source.Item.PixelSize.Height), destRect, BitmapInterpolationMode.Default);
+            DrawBitmap(source, 1, new Rect(0, 0, source.Item.PixelSize.Width, source.Item.PixelSize.Height), destRect, BitmapInterpolationMode.Default, BitmapBlendingMode.SourceOver);
             PopOpacityMask();
         }
 

src/Skia/Avalonia.Skia/SkiaSharpExtensions.cs

@@ -25,6 +25,39 @@ namespace Avalonia.Skia
             }
         }
 
+        public static SKBlendMode ToSKBlendMode(this BitmapBlendingMode blendingMode)
+        {
+            switch (blendingMode)
+            {
+                case BitmapBlendingMode.SourceOver:
+                    return SKBlendMode.SrcOver;
+                case BitmapBlendingMode.Source:
+                    return SKBlendMode.Src;
+                case BitmapBlendingMode.SourceIn:
+                    return SKBlendMode.SrcIn;
+                case BitmapBlendingMode.SourceOut:
+                    return SKBlendMode.SrcOut;
+                case BitmapBlendingMode.SourceAtop:
+                    return SKBlendMode.SrcATop;
+                case BitmapBlendingMode.Destination:
+                    return SKBlendMode.Dst;
+                case BitmapBlendingMode.DestinationIn:
+                    return SKBlendMode.DstIn;
+                case BitmapBlendingMode.DestinationOut:
+                    return SKBlendMode.DstOut;
+                case BitmapBlendingMode.DestinationOver:
+                    return SKBlendMode.DstOver;
+                case BitmapBlendingMode.DestinationAtop:
+                    return SKBlendMode.DstATop;
+                case BitmapBlendingMode.Xor:
+                    return SKBlendMode.Xor;
+                case BitmapBlendingMode.Plus:
+                    return SKBlendMode.Plus;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(blendingMode), blendingMode, null);
+            }
+        }
+
         public static SKPoint ToSKPoint(this Point p)
         {
             return new SKPoint((float)p.X, (float)p.Y);

src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs

@@ -5,6 +5,7 @@ using Avalonia.Platform;
 using Avalonia.Rendering;
 using Avalonia.Rendering.SceneGraph;
 using Avalonia.Utilities;
+using Avalonia.Visuals.Media.Imaging;
 using SharpDX;
 using SharpDX.Direct2D1;
 using SharpDX.Mathematics.Interop;
@@ -116,12 +117,14 @@ namespace Avalonia.Direct2D1.Media
         /// <param name="sourceRect">The rect in the image to draw.</param>
         /// <param name="destRect">The rect in the output to draw to.</param>
         /// <param name="bitmapInterpolationMode">The bitmap interpolation mode.</param>
-        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode)
+        public void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect, BitmapInterpolationMode bitmapInterpolationMode, BitmapBlendingMode bitmapBlendingMode)
         {
             using (var d2d = ((BitmapImpl)source.Item).GetDirect2DBitmap(_deviceContext))
             {
                 var interpolationMode = GetInterpolationMode(bitmapInterpolationMode);
-
+                
+                // TODO: How to implement CompositeMode here?
+                
                 _deviceContext.DrawBitmap(
                     d2d.Value,
                     destRect.ToSharpDX(),
@@ -149,6 +152,35 @@ namespace Avalonia.Direct2D1.Media
             }
         }
 
+        public static CompositeMode GetCompositeMode(BitmapBlendingMode blendingMode)
+        {
+            switch (blendingMode)
+            {  
+                case BitmapBlendingMode.SourceIn:
+                    return CompositeMode.SourceIn;
+                case BitmapBlendingMode.SourceOut:
+                    return CompositeMode.SourceOut;
+                case BitmapBlendingMode.SourceOver:
+                    return CompositeMode.SourceOver;
+                case BitmapBlendingMode.SourceAtop:
+                    return CompositeMode.SourceAtop; 
+                case BitmapBlendingMode.DestinationIn:
+                    return CompositeMode.DestinationIn;
+                case BitmapBlendingMode.DestinationOut:
+                    return CompositeMode.DestinationOut;
+                case BitmapBlendingMode.DestinationOver:
+                    return CompositeMode.DestinationOver;
+                case BitmapBlendingMode.DestinationAtop:
+                    return CompositeMode.DestinationAtop;
+                case BitmapBlendingMode.Xor:
+                    return CompositeMode.Xor;
+                case BitmapBlendingMode.Plus:
+                    return CompositeMode.Plus;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(blendingMode), blendingMode, null);
+            }
+        }
+
         /// <summary>
         /// Draws a bitmap image.
         /// </summary>