[SDL] CVS Update (alpha blending)

Mattias Engdegård f91-men at nada.kth.se
Sun Apr 2 16:41:09 PDT 2000

>Therefore, computationaly it doesn't matter whether the source image is
>32-bit or another format, and in fact since it's cheaper to unpack 32 bpp
>pixels, it's actually faster if the source image is 32 bits per pixel.

Unless the hardware has some magic alpha blit support (DirectX?) that
requires a certain format.

I haven't done enough asm lately to be certain, but I can imagine that
careful use of SIMD instructions can make better code if the format mirrors
the pixel format closely, perhaps blending the RGB components in parallel.

>I'm considering dropping alpha channel support for anything other than
>32-bpp images, although per-surface alpha would still be avaialble.

Isn't ARGB4444 used by Voodoo hardware?

I agree that dropping alpha support for anything but (canonicalized)
32-bit ARGB makes implementation a lot easier, though.

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