NAME

       vtgamma - set gamma correction on text terminals

SYNOPSIS

       vtgamma [-e] [-r] [-l] <gamma>
       vtgamma [-e] [-r] <red gamma> <green gamma> <blue gamma>

DESCRIPTION

       vtgamma  allows  you  to  set  the  gamma  correction  on  Linux console.  It also works on most terminal
       emulators as well.  A good deal of monitors tend to have too dark blue -- human eye is far less sensitive
       to blue light.  This is acceptable for photographic images that should look realistically, but can  cause
       blue, especially dark blue, text to be hard to read.

       vtgamma  is  also useful on aged CRT monitors, which tend to rapidly lose the luminance-to-voltage ratio.
       Even after just 2-3 years, typical CRT often needs gamma of as much as 1.6 to resemble a  new  one.   The
       author of this words has seen a specimen that needed gamma of 2 2 6 (ie, with a big loss of blue) despite
       still having sharp display.

       Gamma correction is given as a positive floating-point number, with 1.0 being the default.

       To affect the login prompt, it's best to: vtgamma 1.6 >>/etc/issue, where 1.6 is the gamma correction you
       want (but see -p).

       Without -p, the color profile lasts either until the next time a program resets the terminal.  While this
       is quite a rare thing, it happens, and thus you'll probably want to have the gamma refreshed every time a
       program exits.  The recommended way is to include vtgamma in PROMPT_COMMAND:

       PROMPT_COMMAND='vtgamma 1.6'

       although  if  you  don't want to spawn a process every prompt, you may instead edit ~/.bashrc and include
       the output of vtgamma -e 1.6 in PS1, enclosed between \[ and \].  Unfortunately, this won't work when you
       switch between terminals using different ways of setting gamma (currently Linux console vs most graphical
       terminals); Midnight Commander can't cope well with prompts containing such codes either.

OPTIONS

       -e|--escape
              Escapes the codes in a form suitable for echo -e, C/Perl/... literals, etc.   You  might  want  to
              include this in /etc/issue.

       -p|--permanent
              On Linux console (VT) only, sets the palette in a way that's permanent until reboot.  This uses an
              ioctl rather than terminal codes, thus can't be captured and written as a string.

       -r|--reverse
              Black  on  white  mode.   Note that this does what you'd expect only on certain terminals, such as
              Linux console.  On most graphical terminal emulators this affects only "real" black and white  but
              not primary text and background colors.

       -l|--lab|--Lab|--lchab|--LCHab
              Uses the LCHab color space (a variant of Lab) instead of RGB, this allows brightening colors above
              FF0000.   Requires  the Graphics::ColorObject library (on Debian, install libgraphics-colorobject-
              perl).

SEE ALSO

       xgamma(1)

AUTHOR

       Both the program and this man page are the fault of Adam Borowski.   Both  of  them  are  in  the  Public
       Domain, or the closest approximation allowed by law.

Debian                                             2006-07-10                                         vtgamma(1)