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       pnmdepth - change the maxval in a portable anymap


       pnmdepth newmaxval [pnmfile]


       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.


       pnm(5), ppmquant(1), ppmdither(1)


       Copyright (C) 1989, 1991 by Jef Poskanzer.

                                 08 April 2000                     pnmdepth(1)