NAME

       vtgamma - set gamma correction on text terminals

SYNOPSIS

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

       You may also select a different palette than default "vga".  A palette  may  then  have  a
       gamma correction applied to it -- all options are allowed.

       This version recognizes the following palettes:

              vga
              gruvbox
              monokai
              ubuntu

       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.