I understood the difference between pixel alpha (the alpha channel for each
pixel) and per-surface alpha. The second one is appliaple on every packed
mode (not in 8.bit mode). But is the seccond appliable only in 32 bit mode?
I don’t have enough bit for the alpha channel in the other modes, isn’it?–
Marco Iannaccone @Marco_Iannaccone
ICQ: 18748121 MetalCoder
"What is real? How do you define real? If you’re talking about your
senses, what you feel, taste, smell, or see, then all you’re talking about
are electrical signals interpreted by your brain."
Morpheus - The Matrix
I don’t know about SDL, but common OpenGL texture pixel formats are RGBA5551
and RGBA4444. There may be other variants as well on some cards… BTW, some
accelerators also support indexed color textures, and consequently, indexed
color + alpha channel pixel formats. (Note: The screen is always in some
packed format, as blending indexed color data is pretty messy. Some software
rasterizers do it, though.)
As long as you’re doing software rendering, you can use any format. How
about RGBA4543? 
The eye is most sensitive to green and red, in that order
(that’s why it’s 565 rather than 655 or 556), while software alpha can be
optimized quite a bit for a small set of alpha levels.)
//David
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
----------------------> http://www.linuxaudiodev.com/maia -' .- David Olofson -------------------------------------------. | Audio Hacker - Open Source Advocate - Singer - Songwriter |--------------------------------------> david at linuxdj.com -'On Tuesday 20 February 2001 01:17, Marco Iannaccone wrote:
I understood the difference between pixel alpha (the alpha channel for each
pixel) and per-surface alpha. The second one is appliaple on every packed
mode (not in 8.bit mode). But is the seccond appliable only in 32 bit mode?
I don’t have enough bit for the alpha channel in the other modes, isn’it?