NAME

       pnmdepth - change the maxval in a portable anymap

SYNOPSIS

       pnmdepth newmaxval [pnmfile]

DESCRIPTION

       Reads  a  portable  anymap  as input.  Scales all the pixel values, and writes out the image with the new
       maxval.  Scaling the colors down to a smaller maxval will result in some loss of information.

       Be careful of off-by-one errors when choosing the new maxval.  For instance, if you want the color values
       to be five bits wide, use a maxval of 31, not 32.

       One  important use of pnmdepth is to convert a new format 2-byte-per-sample PNM file to the older 1-byte-
       per-sample format.  Before April 2000, essentially all raw (binary) format PNM files had  a  maxval  less
       than  256  and  one byte per sample, and many programs may rely on that.  If you specify a newmaxval less
       than 256, the resulting file should be readable by any program that worked with PNM  files  before  April
       2000.

SEE ALSO

       pnm(5), ppmquant(1), ppmdither(1)

AUTHOR

       Copyright (C) 1989, 1991 by Jef Poskanzer.

                                                  08 April 2000                                      pnmdepth(1)