Subject: Re: Visual Modes
To: Al Urbaitis <>
From: Nathan J. Williams <>
List: tech-x11
Date: 11/07/2002 22:21:17
Al Urbaitis <> writes:

> Hello
> Could someone direct me to a discussion
> on Visual Modes. I am interested in the
> difference between "TrueColor" and "DirectColor".

Googling for both of those terms will tell you.

The short version: in both modes the application specifies RGB values
(for example, in a 24-bit mode the application supplies three 8-bit
values) and the video hardware applies lookup tables to convert each
of those R, G, and B values before sending the bits to the D/A
converter of the display.

The difference is that in DirectColor the applicaton can adjust the
lookup tables (for example, to create a different gamma curve); in
TrueColor, the X server and/or hardware has the tables fixed.

Hardware that doesn't support these tables and just feeds the
application's R, G, and B values directly to the D/A converter will
report being in TrueColor mode.

        - Nathan