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List:       linux-video
Subject:    Re: From VIDEO_PALETTE_RGB24 to VIDEO_PALETTE_RGB32
From:       Alexandre <surak () surak ! eti ! br>
Date:       2003-08-27 20:58:40
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Em Qua, 2003-08-27 às 17:17, Joëlle Nakhlé escreveu:
> What is a sdl surface?
> I use 32 bits to display on screen.  The image from the camera is
> stored in a 32 bits bitmap at 30 fps.  I don't know what alpha
> information is, so I can't tell if there is any or not.

SDL stands for Simple Directmedia Layer. It's similar to directdraw in
windows environment. You create a surface (which is a memory area) and
just put your bytes there... sdl takes care of displaying it FAST :-)

As you may know, images use 24 bits for colors. Human eye normally won't
recognize more than this. 32-bit color screen modes wastes 1 byte per
pixel, but is faster because of the simple fact that your computer is
probably optimized for 32-bit thoughput.

Of course, this is not the only scenario. You can also have 24 bits (8
for each color component: r g b) for color and 8 for what they call
ALPHA channel. This extra channel can be used for, say, transparency, a
extra bump map in a 3d surface, or extra data in other forms which
doesn't come to my mind now.

You can find sdl information at your favorite distribution's sdl-devel
package, and at http://www.libsdl.org/



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