NAME

       phisto - compute a luminance histogram from one or more RADIANCE pictures

SYNOPSIS

       phisto picture ..

DESCRIPTION

       Phisto  is  a  script  that calls pfilt(1), rcalc(1) and histo(1) to compute a histogram of log luminance
       values for foveal samples in the given picture files.  A foveal sample  covers  approximately  1  degree,
       though  this script does not use this exact area.  The minimum and maximum values are determined, and 100
       histogram  bins  are  uniformly  divided  between  these  extrema.   Foveal  samples   less   than   1e-7
       candelas/sq.meter  are  silently ignored.  If no picture is named on the command line, the standard input
       is read.

       The primary function of this script is to precompute histograms for the pcond(1) program, which may  then
       be  used  to  compute  multiple, identical exposures.  This is especially useful for animations and image
       comparisons.

EXAMPLE

       To compute two identical tone mappings for image1.hdr and image2.hdr:

         phisto image1.hdr image2.hdr > both.histo
         pcond -I -h image1.hdr < both.histo > image1m.hdr
         pcond -I -h image2.hdr < both.histo > image2m.hdr

AUTHOR

       Greg Ward Larson

SEE ALSO

       histo(1), pcond(1), pfilt(1), pvalue(1), rcalc(1), total(1)

RADIANCE                                             3/12/98                                           PHISTO(1)