1 .\" RCSid "$Id: phisto.1,v 1.4 2008/11/10 19:08:17 greg Exp $"

     2 .TH PHISTO 1 3/12/98 RADIANCE

     3 .SH NAME

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

     5 .SH SYNOPSIS

     6 .B phisto

     7 .B "picture .."

     8 .SH DESCRIPTION

     9 .I Phisto

    10 is a script that calls

    11 .I pfilt(1),

    12 .I rcalc(1)

    13 and

    14 .I histo(1)

    15 to compute a histogram of log luminance values for foveal samples in

    16 the given picture files.

    17 A foveal sample covers approximately 1 degree, though this script does

    18 not use this exact area.

    19 The minimum and maximum values are determined, and 100 histogram bins

    20 are uniformly divided between these extrema.

    21 Foveal samples less than 1e-7 candelas/sq.meter are silently ignored.

    22 If no picture is named on the command line, the standard input is read.

    23 .PP

    24 The primary function of this script is to precompute histograms for the

    25 .I pcond(1)

    26 program, which may then be used to compute multiple, identical exposures.

    27 This is especially useful for animations and image comparisons.

    28 .SH EXAMPLE

    29 .PP

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

    31 .IP "" .2i

    32 phisto image1.hdr image2.hdr > both.histo

    33 .br

    34 pcond \-I \-h image1.hdr < both.histo > image1m.hdr

    35 .br

    36 pcond \-I \-h image2.hdr < both.histo > image2m.hdr

    37 .SH AUTHOR

    38 Greg Ward Larson

    39 .SH "SEE ALSO"

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