public SurfaceImageSourceCanvas(SurfaceImageSource surfaceImageSource, Rect updateRect, Direct2DFactories factories = null)
: base(factories)
{
sisn = ComObject.As<DXGI.ISurfaceImageSourceNative> (surfaceImageSource);
SharpDX.Point offset;
var surface = sisn.BeginDraw (updateRect.ToRectangle (), out offset);
var dpi = 96.0;
var properties = new D2D1.RenderTargetProperties (D2D1.RenderTargetType.Default, new D2D1.PixelFormat (DXGI.Format.Unknown, D2D1.AlphaMode.Unknown), (float)(dpi), (float)(dpi), D2D1.RenderTargetUsage.None, D2D1.FeatureLevel.Level_DEFAULT);
Initialize (new D2D1.RenderTarget (this.factories.D2DFactory, surface, properties));
}
