unu gamma: Brighten or darken values with a gamma. Just as in xv, the gamma
value here is actually the reciprocal of the exponent actually used to
transform the values.
Usage: unu gamma -g <gamma> [-min <value>] [-max <value>] [-i <nin>] \
[-o <nout>]
-g <gamma> = gamma > 1.0 brightens; gamma < 1.0 darkens. Negative gammas
invert values (like in xv). (double)
-min <value> = Value to implicitly map to 0.0 prior to calling pow().
Defaults to lowest value found in input nrrd. (double)
-max <value> = Value to implicitly map to 1.0 prior to calling pow().
Defaults to highest value found in input nrrd. (double)
-i <nin> = input nrrd
-o <nout> = output nrrd (string); default: "-"
