Implemented bitmap render target for new skia backend

src/Skia/Perspex.Skia.Desktop/Perspex.Skia.Desktop.csproj

@@ -38,7 +38,7 @@
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
     <DebugSymbols>true</DebugSymbols>
     <OutputPath>bin\x86\Debug\</OutputPath>
-    <DefineConstants>TRACE;DEBUG;WIN32</DefineConstants>
+    <DefineConstants>TRACE;DEBUG;WIN32;DESKTOP</DefineConstants>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DebugType>full</DebugType>
     <PlatformTarget>x86</PlatformTarget>
@@ -47,7 +47,7 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
     <OutputPath>bin\x86\Release\</OutputPath>
-    <DefineConstants>TRACE;WIN32</DefineConstants>
+    <DefineConstants>TRACE;WIN32;DESKTOP</DefineConstants>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <Optimize>true</Optimize>
     <DebugType>pdbonly</DebugType>
@@ -62,6 +62,7 @@
     </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
+    <Reference Include="System.Drawing" />
     <Reference Include="System.Xml.Linq" />
     <Reference Include="System.Data.DataSetExtensions" />
     <Reference Include="Microsoft.CSharp" />

src/Skia/Perspex.Skia/BitmapImpl.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Drawing.Imaging;
 using System.IO;
 using System.Runtime.InteropServices;
 using System.Text;
@@ -22,39 +23,62 @@ namespace Perspex.Skia
 
         public BitmapImpl(int width, int height)
         {
-            throw new NotImplementedException();
+            PixelHeight = height;
+            PixelWidth = width;
+            Bitmap = new SKBitmap(width, height, SKColorType.N_32, SKAlphaType.Premul);
         }
 
         public void Dispose()
         {
+            Bitmap.Dispose();
         }
 
         public void Save(string fileName)
         {
-            // TODO: Implement this for SkiaSharp
-            throw new NotImplementedException();
-
-            //var ext = Path.GetExtension(fileName)?.ToLower();
-            //var type = MethodTable.SkiaImageType.Png;
-            //if(ext=="gif")
-            //    type = MethodTable.SkiaImageType.Gif;
-            //if(ext=="jpeg" || ext =="jpg")
-            //    type = MethodTable.SkiaImageType.Jpeg;
-            //var skdata = MethodTable.Instance.SaveImage(Handle, type, 100);
-            //var size = MethodTable.Instance.GetSkDataSize(skdata);
-            //var buffer = new byte[size];
-            //MethodTable.Instance.ReadSkData(skdata, buffer, size);
-            //File.WriteAllBytes(fileName, buffer);
+#if DESKTOP
+            IntPtr length;
+            using (var sdb = new System.Drawing.Bitmap(PixelWidth, PixelHeight, Bitmap.RowBytes,
+                PixelFormat.Format32bppArgb, Bitmap.GetPixels(out length)))
+                sdb.Save(fileName);
+#else
+            //SkiaSharp doesn't expose image encoders yet
+#endif
         }
 
         public int PixelWidth { get; private set; }
         public int PixelHeight { get; private set; }
 
+        class BitmapDrawingContext : DrawingContextImpl
+        {
+            private readonly SKSurface _surface;
+
+            public BitmapDrawingContext(SKBitmap bitmap) : this(CreateSurface(bitmap))
+            {
+                
+            }
+
+            private static SKSurface CreateSurface(SKBitmap bitmap)
+            {
+                IntPtr length;
+                return SKSurface.Create(bitmap.Info, bitmap.GetPixels(out length), bitmap.RowBytes);
+            }
+
+            public BitmapDrawingContext(SKSurface surface) : base(surface.Canvas)
+            {
+                _surface = surface;
+            }
+
+            public override void Dispose()
+            {
+                base.Dispose();
+                _surface.Dispose();
+            }
+        }
+
         public DrawingContext CreateDrawingContext()
         {
-            return
-                new DrawingContext(
-                    new DrawingContextImpl(null));	// MethodTable.Instance.RenderTargetCreateRenderingContext(Handle)));
+
+            return new DrawingContext(new BitmapDrawingContext(Bitmap));
         }
 
     }