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gangliu

how to implement high efficient alpha Channel ?

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hello all: I have two DirectDraw Surfaces( bmp and alpha Channel ). How Can I implement alpha Channel by bit operation . because DirectDraw don't provide the function . The Msdn describes : The IDirectDrawSurface7::Blt method performs a bit block transfer (blit). This method does not support z-buffering or alpha blending (see alpha channel) during blit operations. I attempt to draw pixel by piexl, the efficiency is poor. Thanks for any advice. Thanks for your help.

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Your 2 basic choices are:
1)Keep your surfaces in System memory, do your blending with cunning assembly (MMX, etc) then blit the final result to the backbuffer

2)Use Direct3D since Alphablending is essentially free.

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