# phpman > info > pnmdepth

[pnmdepth(1)](https://www.chedong.com/phpMan.php/man/pnmdepth/1/markdown)                 General Commands Manual                [pnmdepth(1)](https://www.chedong.com/phpMan.php/man/pnmdepth/1/markdown)

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 in-
       stance, 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)](https://www.chedong.com/phpMan.php/man/pnm/5/markdown), [ppmquant(1)](https://www.chedong.com/phpMan.php/man/ppmquant/1/markdown), [ppmdither(1)](https://www.chedong.com/phpMan.php/man/ppmdither/1/markdown)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.

                                 08 April 2000                     [pnmdepth(1)](https://www.chedong.com/phpMan.php/man/pnmdepth/1/markdown)