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)