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Tooon

MMX Saturation in 16bpp

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Hi all! Im just finished with by 32bpp blitroutines using MMX. Saturation, Alphablending etc is pretty easy to do in 32bpp, but how can you get advantage of MMX using 16bpp? If anyone could give me a hint adding two pixles together in 16bpp with saturation and MMX I would be very grateful! Cheers / Tooon

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OK, will not packed word aremetic just make sure that
the word it self wont overflow? I need an algoritm wich adds each attribute of R,G,B so R cant for example be larger than 32, green 64 etc etc...

if we have the color (R=31, G=0, B=31) in a word, adding color (R=31,G=63,B=31) should result in (R=31, G=63, B=31).

In 32bpp each attribute is stored in a specific byte and has
a max value of 255, wich makes this procedure easy to accomplish (paddusb).

Don''t know if I should bother using MMX for this, or if it will just be as fast using "normal" asm methods.

/ Tooon




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Ah, I didn't read your post carefully enough. I couldn't think of an elegant way either. Here's my best guess.

You'll have to pardon quasi-MMX

[Assume 5 - 5 - 5 ]


movq MM0,[ESI]
movq MM2,MM0
movq MM3,MM0
movq MM4,MM0
and MM2, REDFILTER
PSHRB MM3,5
and MM3, REDFILTER //The green colors
PSHRB MM4, 10
and MM4, REDFILTER //The blue colors


At this point, all the colors are low-bit-aligned in their word. Each register (MM2 - MM4) contains 4 pixels, each with a single color component.

Edited by - WMiller on May 10, 2000 5:02:32 PM

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