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)