PHISTO(1)						      General Commands Manual							 PHISTO(1)

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 max-
       imum  values  are  determined,  and  100  histogram bins are uniformly divided between these extrema.  Foveal samples less than 1e-7 cande-
       las/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, iden-
       tical 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)