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 within the range 0 to 255.  However, a color with r, g, and b components of 128 is not 50 percent gray.  On the monitor, this gray appears 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 used by gammapcolor is stored in ~/.gamma . 

gamma followed by a floating point argument sets the gamma correction value.  gamma with no arguments prints the current gamma correction value.  For a discussion of gamma correction, see Fundamentals of Interactive Computer Graphics by James D. Foley and Andries Van Dam (Addison-Wesley Publishing Company, 1982), pp. 594-597. 

FILES

~/.gamma

Version 2.5r1  —  October 29, 1986