Unexpected xcalib applications #1: preserving night vision

It's been a while since I have done work on xcalib or posted here on this blog but I have a little bit problems with jetlag currently, which provides me with a little bit of extra time. So, I've done a little google research on where xcalib is used in scenarios that haven't been envisioned when I wrote xcalib.

Application #1: Making the screen red to preserve night vision
(from here: http://ubuntuforums.org/showpost.php?p=6803029&postcount=4 - by sanskaras)

The trick is basically to switch off green and blue entirely. The proposed solution is modifying these two channels with the -green and -blue command line paramters. I've realized that these quite powerful commands are not documented in the README currently, hence here's the description:

-green GREENGAMMA GREENBRIGHTNESS GREENCONTRAST
-blue BLUEGAMMA BLUEBRIGHTNESS BLUECONTRAST
-red REDGAMMA REDBRIGHTNESS REDCONTRAST

With these switches and the -alter command it is possible to modify the existing color behavior.

Hence, the following is, according to the link, a possible setting for disabling green and blue.

Code:

xcalib -green .1 0 1 -alter
xcalib -blue .1 0 1 -alter

These are the currently lowest allowed parameters in xcalib, hence it's well possible that I remove these limits in future versions or add a parameter to disable a channel entirely.

When all is over or the screen became unreadable, you can always revert back to normal:

Code:

xcalib -clear