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)