pnmdepth

Pnmdepth User Manual(0)                                Pnmdepth User Manual(0)

NAME

       pnmdepth - change the maxval in a PNM image

SYNOPSIS

       pnmdepth

       newmaxval

       [pnmfile]

DESCRIPTION

       This program is part of Netpbm(1).

       pnmdepth  reads  a PNM image 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(1), pnmquant(1), ppmdither(1)

AUTHOR

       Copyright (C) 1989, 1991 by Jef Poskanzer.



netpbm documentation             08 April 2000         Pnmdepth User Manual(0)