Tremulous Forum

General => General Discussion => Topic started by: nalf on February 09, 2012, 09:38:35 am

Title: Altering gamma under Linux
Post by: nalf on February 09, 2012, 09:38:35 am

Somebody asked yesterday how to alter gamma on GPP under Linux. Apparently, the menu option doesn't work. I googled somewhere that it can be done by the xgamma (http://manpages.ubuntu.com/manpages/gutsy/man1/xgamma.1x.html) command line tool. For example

Code: [Select]

xgamma -gamma 1.7and setting it back to normal:

Code: [Select]

xgamma -gamma 1It changes the whole Xorg system though, so all applications are affected.
One can use a simple shell script to start GPP with altered gamma:

Code: (shell) [Select]

#!/bin/sh
xgamma -gamma 1.7 # alter the value to your needs
trap "xgamma -gamma 1" EXIT
# change the path to your tremgpp installatin
~/game/tremulous/tremulous-gpp.x86 "$@"

I found some other tools that possibly allow to change brightness and contrast: DDCcontrol (http://ddccontrol.sourceforge.net/), xvattr (http://freecode.com/projects/xvattr), but they don't work for me (depends on a graphics chip/driver I suppose). If you have better luck, let others know.

And there is also another program Redshift (http://jonls.dk/redshift/) that alters automatically perceived display color depending on current daytime. Can help strained eyes if playing/working too long.

Update: I found out that gamma can be also corrected by the xrandr (http://www.x.org/wiki/Projects/XRandR) tool. It allows to change both gamma and brightness. First  query your configuration by

Code: [Select]

xrandr --queryand then alter the parameters for your selected output (mine is LVDS):

Code: [Select]

xrandr --output LVDS --gamma 0.5:0.5:0.5 --brightness 1.5and set it back

Code: [Select]

xrandr --output LVDS --gamma 1:1:1 --brightness 1The brightness correction is only software based, as the documentation says:

Quote

However,  this  is a software only modification, if your hardware has support to actually change the brightness, you will probably  prefer  to  use xbacklight (http://linux.die.net/man/1/xbacklight).

Title: Re: Altering gamma under Linux
Post by: Qrntz on February 09, 2012, 12:47:15 pm

It's better to just specify

Code: [Select]

--output default
in the XrandR command line.
This way it manages whatever display is your current one.

Title: Re: Altering gamma under Linux
Post by: Tremulant on February 09, 2012, 06:59:35 pm

Quote from: Qrntz on February 09, 2012, 12:47:15 pm

It's better to just specify

Code: [Select]

--output default
in the XrandR command line.
This way it manages whatever display is your current one.

Assuming it happens to actually be called "default"? or does this actually work as you suggest in more modern versions of xrandr than i've got?

Title: Re: Altering gamma under Linux
Post by: Qrntz on February 10, 2012, 02:19:04 am

Quote from: Tremulant on February 09, 2012, 06:59:35 pm

Quote from: Qrntz on February 09, 2012, 12:47:15 pm

It's better to just specify

Code: [Select]

--output default
in the XrandR command line.
This way it manages whatever display is your current one.

Assuming it happens to actually be called "default"? or does this actually work as you suggest in more modern versions of xrandr than i've got?

Yes, this actually modifies the default output, be it VGA, LVDS, TV or else. My version is 1.3.2 and I just checked if this still works (it does).
I don't ever use xrandr for gamma correction though, for
1) I am lucky enough to not need gamma correction
2) it doesn't play nice with the nvidia proprietary drivers, which stopped bothering about xrandr's existance since it was 1.1. See:

Code: [Select]

xrandr: Failed to get size of gamma for output defaultPeople with proprietary nvidia drivers should use the nvidia-settings app to tweak gamma.

Title: Re: Altering gamma under Linux
Post by: Little*Butterfly on February 29, 2012, 11:25:45 am

Hi,

Try this in the console

/r_ignorehwgamma 1
/r_gamma 2.0

Try 0 and 1 for r_ignorehwgamma