Re: [Linux-fbdev-devel] directcolor

[James S. <jsi...@li...>]

>I have writen a prog, which works perfectly on a g400 card, which uses
>truecolor visual, but it makes a really strange looking picture on an
>ATI XPert@Work card, which uses directcolor.
>so what does the directcolor mean?
>or is there a document about fbdev for programmers?
>I only found a howto for users...

Direct color is when a pixel value is decomposed into three seperate
subfields for colormap indexing. One subfield indexes an array to produce
red intensity values; second subfield indexes a second array to produce
green intensity values etc.

Truecolor represnts multiplane displays with predefinded and read only RGB
values in its hardware colormap. Here pixel values directly encode into
corresponding RGB values.

What does this mean? For truecolor if want white you set all the feilds
RGB to the maximum value. What if that white is not white enough for you.
For truecolor you are out of luck. For direct color you can change the
range of intensities for the RGB feilds. This way we can get a brighter
white.

P.S
  A neat side note. Thier is a staturation limit to colors in color theory.
You can only make white so bright and no matter how much equal amounts of
red, blue, and green you add it doesn't get any brighter.


MS: (n) 1. A debilitating and surprisingly widespread affliction that
renders the sufferer barely able to perform the simplest task. 2. A disease.

James Simmons  [jsi...@li...]               ____/|
fbdev/console/gfx developer                             \ o.O|
http://www.linux-fbdev.org                               =(_)=
http://linuxgfx.sourceforge.net                            U
http://linuxconsole.sourceforge.net