AW: Implementing PseudoColor support on TrueColor screens

[Walter Harms]

the correct way to do is use XPutPixel().
color these days if pretty easy  color=0/r/g/b

You need a lookuptable for 256 colors (=st2d_8to24table[i] ?)
and that should it be.

re,
 wh

________________________________________
Von: xorg <xorg-bounces at lists.x.org> im Auftrag von Sleep <ireallyhatespam at yandex.com>
Gesendet: Dienstag, 2. Juni 2020 08:28:13
An: xorg at lists.x.org
Betreff: Implementing PseudoColor support on TrueColor screens

Is there any documentation, article or book on how to convert the colors
displayed by a program that was originally written to work on 8 bit
screens? The problem I am facing seems to be related to how pixels are
represented in the 'data' member of the XImage structure, which results
in a squashed image and colors being displayed incorrectly. The only
reference I have are two functions in the Quake source code:
xlib_rgb24()[1] and st3_fixup()[2], which are used to convert the colors
(but I cannot comprehend them because the format is unknown to me), but
I found nothing that could make the image fill the window[3] properly. I
could use SDL to easily get around this issue but I specifically want to
use Xlib.

I appreciate any help to learn.

[1]
<https://github.com/id-Software/Quake/blob/bf4ac424ce754894ac8f1dae6a3981954bc9852d/WinQuake/vid_x.c#L156>
[2]
<https://github.com/id-Software/Quake/blob/bf4ac424ce754894ac8f1dae6a3981954bc9852d/WinQuake/vid_x.c#L219>
[3] https://postimg.cc/MfRz0Dk7
[4] https://i.postimg.cc/brVdhC3B/doom.png
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