NAME

       pgmtoppm - colorize a portable graymap into a portable pixmap

SYNOPSIS

       pgmtoppm colorspec [pgmfile]
       pgmtoppm colorspec1-colorspec2 [pgmfile]
       pgmtoppm -map mapfile [pgmfile]

DESCRIPTION

       Reads a PGM as input.  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 dash), then black gets mapped to the first  color  and
       white  gets  mapped  to  the  second  and  gray  values  in  between  get mapped linearly (across a three
       dimensional space) to colors in between.

       You can specify the color in one of five ways:

       o      A name, from an X11-style color names file.

       o      An X11-style hexadecimal specifier: rgb:r/g/b, where r g and b are each 1- to 4-digit  hexadecimal
              numbers.

       o      An  X11-style  decimal specifier: rgbi:r/g/b, where r g and b are floating point numbers between 0
              and 1.

       o      For backwards compatibility, an old-X11-style hexadecimal number: #rgb,  #rrggbb,  #rrrgggbbb,  or
              #rrrrggggbbbb.

       o      For  backwards compatibility, a triplet of numbers separated by commas: r,g,b, where r g and b are
              floating point numbers between 0 and 1.  (This style was added before MIT came up with the similar
              rgbi style.)

       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.

NOTE - MAXVAL

       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 (in fact, let's say it's a  PBM  file,  since  pgmtoppm,
       like  all  Netpbm  programs,  can  accept  a  PBM file as if it were PGM.  The maxval of this image is 1,
       because only two gray values are needed: black and white.  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 pnmdepth 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,  pnmdepth
       16 would do it.  Or spare yourself the unnecessary thinking and just say pnmdepth 255 .

SEE ALSO

       pnmdepth(1), rgb3toppm(1), ppmtopgm(1), ppmtorgb3(1), ppm(5), pgm(5)

AUTHOR

       Copyright (C) 1991 by Jef Poskanzer.

                                                 24 January 2001                                     pgmtoppm(1)