The Code：
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dsuf.DrawAdd(DestRect, SrcRect,ssuf,true, 255) ;{not work of FullScreen,but work good in Window model}
................
var
  d: TDirectDrawSurface;
  rc: TRect;,
...........
dsurface.DrawAlpha(rc,d.ClientRect, d, True, 200);//No Work
.....................
The Pic.bmp is 8 Bit 256 Color. Transparent color is clBlack 00000000
Thanks!