DirectDraw supports source and destination color keying for blits and overlay surfaces. Color keys enable you to display one image on top of another selectively, so that only certain pixels from the foreground rectangle are displayed, or only certain pixels on the background rectangle are overwritten.
You supply a single color key or a range of colors for source or destination color keying by calling the IDirectDrawSurface4::SetColorKey method.
For more information about color keying, see the following topics: