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.