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Pgmtoppm User Manual(0) 						  Pgmtoppm User Manual(0)

NAME
       pgmtoppm - colorize a PGM (grayscale) image into a PPM (color) image

SYNOPSIS
       pgmtoppm  colorspec  [pgmfile] pgmtoppm colorspec1-colorspec2 [pgmfile] pgmtoppm -map=map-
       file [pgmfile]

       Minimum unique abbreviation of option is acceptable.  You may use double  hyphens  instead
       of  single  hyphen to denote options.  You may use white space in place of the equals sign
       to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1)

       pgmtoppm reads a PGM as input and produces a PPM file as  output  with  a  specific  color
       assigned to each gray value in the input.

       If  you specify one color argument, black in the pgm file stays black and white in the pgm
       file turns into the specified color in the ppm file.  Gray values in between are  linearly
       mapped to differing intensities of the specified color.

       If  you specify two color arguments (separated by a hyphen), then black gets mapped to the
       first color and white gets mapped to the second and gray values in between get mapped lin-
       early (across a three dimensional space) to colors in between.

       Specify	the  color  (color) as described for the argument of the ppm_parsecolor() library
       routine <libppm.html#colorname> .

       Also, you can specify an entire colormap with the -map option.  The mapfile is just a  ppm
       file;  it can be any shape, all that matters is the colors in it and their order.  In this
       case, black gets mapped into the first color in the map file, and white gets mapped to the
       last  and  gray	values	in  between  are  mapped  linearly onto the sequence of colors in
       between.  The maxval of the output image is the maxval of the map image.

       A more direct way to specify a particular color to replace each particular gray	level  is
       to  use	pamlookup.   You  make an index file that explicitly associates a color with each
       possible gray level.

NOTE - MAXVAL
       When you don't use -map, the 'maxval,' or depth, of the output image is the same  as  that
       of the input image.  The maxval affects the color resolution, which may cause quantization
       errors you don't anticipate in your output.  For example, you  have  a  simple  black  and
       white  image  as  a PGM with maxval 1.  Run this image through pgmtoppm 0f/00/00 to try to
       make the image black and faint red.  Because the output image will  also  have  maxval  1,
       there  is no such thing as faint red.  It has to be either full-on red or black.  pgmtoppm
       rounds the color 0f/00/00 down to black, and you get an output image that is  nothing  but
       black.

       The  fix is easy: Pass the input through pamdepth on the way into pgmtoppm to increase its
       depth to something that would give you the resolution you need to get your desired  color.
       In  this  case,	pamdepth  16 would do it.  Or spare yourself the unnecessary thinking and
       just say pamdepth 255.

       PBM input is a special case.  While you might think this would be equivalent to a PGM with
       maxval 1 since only two gray levels are necessary to represent a PBM image, pgmtoppm, like
       all Netpbm programs, in fact treats it as a maxval of 255.

SEE ALSO
       pamdepth(1) , rgb3toppm(1) , ppmtopgm(1) , ppmtorgb3(1) , ppm(1) , pgm(1)

AUTHOR
       Copyright (C) 1991 by Jef Poskanzer.

netpbm documentation			 10 December 2006		  Pgmtoppm User Manual(0)
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