CentOS 7.0 - man page for sdl_setgamma (centos section 3)

SDL_SetGamma(3) 			SDL API Reference			  SDL_SetGamma(3)

NAME
       SDL_SetGamma - Sets the color gamma function for the display

SYNOPSIS
       #include "SDL.h"

       int SDL_SetGamma(float redgamma, float greengamma, float bluegamma);

DESCRIPTION
       Sets  the  "gamma  function"  for  the display of each color component. Gamma controls the
       brightness/contrast of colors displayed on the screen. A gamma value of	1.0  is  identity
       (i.e., no adjustment is made).

       This  function adjusts the gamma based on the "gamma function" parameter, you can directly
       specify lookup tables for gamma adjustment with SDL_SetGammaRamp.

       Not all display hardware is able to change gamma.

RETURN VALUE
       Returns -1 on error (or if gamma adjustment is not supported).

SEE ALSO
       SDL_GetGammaRamp SDL_SetGammaRamp

SDL				      Tue 11 Sep 2001, 23:01			  SDL_SetGamma(3)