phpman > man > pnmdepth(1)

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  in‐
       formation.

       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 pro‐
       gram 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)