pgmtoppm(1)                                                   General Commands Manual                                                  pgmtoppm(1)

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 reso-
       lution 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)