NAME

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

SYNOPSIS

       pgmtoppm [-black=colorspec1] [-white=colorspec2]
        [pgmfile]  pgmtoppm  -map=filename [pgmfile] pgmtoppm colorspec [pgmfile] pgmtoppm colorspec1-colorspec2
       [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).

       If all you want to do is convert PGM to PPM, keeping the same gray pixels,
         you may not need to.  All Netpbm programs that expect PPM input also
         recognize PGM.  And if you must have a PPM file, use ppmtoppm
         instead.  It is more efficient and easier to use.

       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.

       You can specify the color in the output to which black in the input maps,
         and the color to which white maps.  All the gray values in between map
         linearly (across a three dimensional space) to colors between the black and
         white colors you specify.

       Use the -black and -white options for this.  For historical
         reasons, you can alternatively use a non-option argument to specify the
         colors.  If you do that, pgmtoppm interprets the color argument
         like this: if the argument takes the form black-white,
         it has the effect of -black=black -white=white
         If instead there is no hyphen in the color argument, it has the effect of
         -white=color_argument.

       Because of the historical syntax, it is not possible to let both
         -black and -white default (but you shouldn't want to --
         see below for advice on making such a null conversion).

       You can alternatively specify an entire colormap with the -map option.

       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.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet, see
        Common Options ⟨index.html#commonoptions⟩ ), pgmtoppm recognizes the following command line options:

       -black=colorspec
              The program maps black pixels in the input to this color in the output.  The default is black.

              Specify the color (color) as described for the argument of the  pnm_parsecolor()  library  routine
              ⟨libnetpbm_image.html#colorname⟩ .

              You cannot specify this together with -map.

              This option was new in Netpbm 10.97 (December 2021).  Before that,
                use the color argument.

       -white=colorspec
              The program maps white pixels in the input to this color in the output.  The default is white.

              Specify  the  color  (color) as described for the argument of the pnm_parsecolor() library routine
              ⟨libnetpbm_image.html#colorname⟩ .

              You cannot specify this together with -map.

              This option was new in Netpbm 10.97 (December 2021).  Before that,
                use the color argument.

       -map=filename
              This option specifies a complete mapping of gray values in the input to
                  color values in the output.  The map file (named filename) 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.

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

       ppmtoppm(1), pamdepth(1), rgb3toppm(1), ppmtopgm(1), ppmtorgb3(1), ppm(1), pgm(1)

AUTHOR

       Copyright (C) 1991 by Jef Poskanzer.

DOCUMENT SOURCE

       This  manual  page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation
       is at

              http://netpbm.sourceforge.net/doc/pgmtoppm.html