php man page for pnmdepth

pnmdepth(1)						      General Commands Manual						       pnmdepth(1)

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  max-
       val 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)