public static void FillRectangleAlpha(Graphics graphic, Brush brush, int left, int top, int width, int height, int transparency)
{
if (_workGraphics == null)
{
_workBitmap = new Bitmap(1024, 1024, System.Drawing.Imaging.PixelFormat.Format16bppRgb565);
_workGraphics = Graphics.FromImage(_workBitmap);
}
_workGraphics.FillRectangle(brush, 0, 0, width, height);
PlatformAPIs.DrawAlpha(graphic, _workBitmap, (byte)transparency, left, top, width, height);
}
public static void DrawAlpha(Graphics gx, Bitmap image, byte transp, int x, int y, int width, int height)
{
using (Graphics gxSrc = Graphics.FromImage(image))
{
IntPtr hdcDst = gx.GetHdc();
IntPtr hdcSrc = gxSrc.GetHdc();
BlendFunction blendFunction = new BlendFunction();
blendFunction.BlendOp = (byte)BlendOperation.AC_SRC_OVER; // Only supported blend operation
blendFunction.BlendFlags = (byte)BlendFlags.Zero; // Documentation says put 0 here
blendFunction.SourceConstantAlpha = transp; // Constant alpha factor
blendFunction.AlphaFormat = (byte)0; // Don't look for per pixel alpha
PlatformAPIs.AlphaBlend(hdcDst, x, y, width, height, hdcSrc, 0, 0, width, height, blendFunction);
gx.ReleaseHdc(hdcDst); // Required cleanup to GetHdc()
gxSrc.ReleaseHdc(hdcSrc); // Required cleanup to GetHdc()
}
}
