NAME

gamma − set the gamma correction value for mapping colors

SYNOPSIS

gamma newgamma

DESCRIPTION

The luminous intensity displayed by the monitor is a power function of the input drive voltage.  When a color index is mapped using mapcolor(index,r,g,b), the red, green, and blue drive voltages are specified using a range of 0 to 255.  However, it is wrong to assume that a color with r, g, and b components of 128 is a 50 percent grey.  On the monitor this grey will appear considerably darker because the luminous intensity is not linearly related to drive voltage.  /usr/people/gifts/mextools/portlib provides the function gammapcolor(i,r,g,b) to correct for the non-linearity of the display.  The gamma correction value is stored in ~/.gamma .  This value will be used by the gammapcolor function.  gamma followed by a floating point argument sets the gamma correction value.  gamma with no arguments prints the current gamma correction value.  See pages 594-597 of Foley and Van Dam, Fundamentals of Interactive Computer Graphics, for a discussion of gamma correction. 

FILES

~/.gamma

Version 2.4  —  May 08, 1986