public static WriteableBitmap Overlay(WriteableBitmap bmp, WriteableBitmap overlay, Point location)
{
var result = bmp.Clone();
var size = new Size(overlay.PixelWidth, overlay.PixelHeight);
result.Blit(new Rect(location, size), overlay, new Rect(new Point(0, 0), size), WriteableBitmapExtensions.BlendMode.Alpha);
return result;
}
