Added debugging util to save D2D render targets.

src/Windows/Avalonia.Direct2D1/Media/Imaging/D2DRenderTargetBitmapImpl.cs

@@ -1,8 +1,10 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using System.IO;
 using Avalonia.Platform;
 using Avalonia.Rendering;
+using Avalonia.Utilities;
 using SharpDX;
 using SharpDX.Direct2D1;
 using D2DBitmap = SharpDX.Direct2D1.Bitmap;
@@ -49,5 +51,22 @@ namespace Avalonia.Direct2D1.Media.Imaging
         {
             return new OptionalDispose<D2DBitmap>(_renderTarget.Bitmap, false);
         }
+
+        public override void Save(Stream stream)
+        {
+            using (var wic = new WicRenderTargetBitmapImpl(PixelSize, Dpi))
+            {
+                using (var dc = wic.CreateDrawingContext(null))
+                {
+                    dc.DrawImage(
+                        RefCountable.CreateUnownedNotClonable(this),
+                        1,
+                        new Rect(PixelSize.ToSize(Dpi.X)),
+                        new Rect(PixelSize.ToSize(Dpi.X)));
+                }
+
+                wic.Save(stream);
+            }
+        }
     }
 }

src/Windows/Avalonia.Direct2D1/Utils/DebugUtils.cs

@@ -0,0 +1,13 @@
+using Avalonia.Direct2D1.Media.Imaging;
+
+namespace Avalonia.Direct2D1.Utils
+{
+    internal static class DebugUtils
+    {
+        public static void Save(SharpDX.Direct2D1.BitmapRenderTarget bitmap, string filename)
+        {
+            var rtb = new D2DRenderTargetBitmapImpl(bitmap);
+            rtb.Save(filename);
+        }
+    }
+}