add a proposed GetPixels method to IBitmapImpl with skia implementation.

src/Avalonia.Visuals/Platform/IBitmapImpl.cs

@@ -1,6 +1,7 @@
 // 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;
 using System.IO;
 
 namespace Avalonia.Platform
@@ -31,5 +32,11 @@ namespace Avalonia.Platform
         /// </summary>
         /// <param name="stream">The stream.</param>
         void Save(Stream stream);
+
+        /// <summary>
+        /// Gets a pointer to the pixel data.
+        /// </summary>
+        /// <returns>IntPtr to the pixel data.</returns>
+        IntPtr GetPixels();
     }
 }

src/Skia/Avalonia.Skia/BitmapImpl.cs

@@ -23,6 +23,7 @@ namespace Avalonia.Skia
         static void ReleaseProc(IntPtr address, object ctx)
         {
             ((IUnmanagedBlob) ctx).Dispose();
+            
         }
 
         private static readonly SKBitmapReleaseDelegate ReleaseDelegate = ReleaseProc;
@@ -60,6 +61,11 @@ namespace Avalonia.Skia
         public int PixelWidth { get; private set; }
         public int PixelHeight { get; private set; }
 
+        public IntPtr GetPixels()
+        {
+            return Bitmap.GetPixels();
+        }
+
         class BitmapDrawingContext : DrawingContextImpl
         {
             private readonly SKSurface _surface;