ppmtogif - convert a portable pixmap into a GIF file


SYNOPSIS

       ppmtogif [-interlace] [-sort] [-map mapfile] [-transparent
       [=]color] [-comment text]

       [ppmfile]

       All options can be abbreviated to  their  shortest  unique
       prefix.


DESCRIPTION

       Reads  a portable pixmap as input.  Produces a GIF file as
       output.

       This program creates only individual GIF images.  To  com­
       bine  multiple GIF images into an animated GIF, use gifsi­
       cle.

       ppmtogif creates either an original GIF87 format GIF  file
       or  the  newer  GIF89  format.   It creates GIF89 when you
       request features that were new  with  GIF89,  to  wit  the
       -transparent  or  -comment options.  Otherwise, it creates
       GIF87.  Really old GIF readers conceivably could not  rec­
       ognize GIF89.


OPTIONS

       -interlace
              Produce an interlaced GIF file.

       -sort  Produces a GIF file with a sorted color map.

       -map   mapfile

              Uses  the colors found in the mapfile to create the
              colormap in the GIF file,  instead  of  the  colors
              from ppmfile.  The mapfile can be any ppm file; all
              that matters is the colors in it. If the colors  in
              ppmfile  do  not  match those in mapfile , they are
              matched to a "best match." A (much)  better  result
              can  be  obtained  by using the following filter in
              advance:

              ppmquant -floyd -map mapfile

       -transparent color
              Mark the given color  as  transparent  in  the  GIF
              file.  The color is specified as in ppmmake(1).  If
              the color you specify is not present in the  image,
              ppmtogif  selects  instead  the  color in the image

              is  measured as a cartesian distance between colors
              in RGB space.  If multiple colors are  equidistant,
              ppmtogif chooses one of them arbitrarily.

              However,  if  you  prefix  your color specification
              with "=", e.g.

              -transparent==red

              Only the exact color you specify will be  transpar­
              ent.   If  that color does not appear in the image,
              there will be no transparency.  ppmtogif issues  an
              information message when this is the case.

       -comment text
              Include  a  comment  in the GIF output with comment
              text text.  Without this option, there are no  com­
              ments in the output.


SEE ALSO

       giftopnm(1),    ppmquant(1),    pngtopnm(1),   gifsicle(1)
       <http://www.lcdf.org/gifsicle>, ppm(5).


AUTHOR

       Based on GIFENCOD by David  Rowley  <mgardi@watdcsu.water­
       loo.edu>.  Lempel-Ziv compression based on "compress".

       Copyright (C) 1989 by Jef Poskanzer.


LICENSE

       If  you  use  ppmtogif,  you are using a patent on the LZW
       compression method which is owned by Unisys,  and  in  all
       probability  you  do  not have a license from Unisys to do
       so.  Unisys typically asks $5000 for a license for trivial
       use  of  the patent.  Unisys has never enforced the patent
       against trivial users.  The patent expires in 2003.

       Rumor has it that IBM also owns  a  patent  covering  ppm­
       togif.

       A replacement for the GIF format that does not require any
       patents to use is the PNG format.


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