giftopnm

giftopnm(1)                 General Commands Manual                giftopnm(1)

NAME
       giftopnm - convert a GIF file into a portable anymap

SYNOPSIS
       giftopnm [--alphaout={alpha-filename,-}] [-verbose] [-comments] [-image
       N] [GIFfile]

DESCRIPTION
       This is a graphics format converter from the  GIF  format  to  the  PNM
       (i.e. PBM, PGM, or PPM) format.

       If the image contains only black and maximally bright white, the output
       is PBM.  If the image contains more than those  two  colors,  but  only
       grays, the output is PGM.  If the image contains other colors, the out-
       put is PPM.

       If you have an animated GIF file, you  can  extract  individual  frames
       from it with gifsicle and then convert those using giftopnm.

       A GIF image contains rectangular pixels.  They all have the same aspect
       ratio, but may not be square (it's actually quite unusual for them  not
       to  be  square, but it could happen).  The pixels of a Netpbm image are
       always square.  Because of the engineering complexity to do  otherwise,
       giftopnm  converts a GIF image to a Netpbm image pixel-for-pixel.  This
       means if the GIF pixels are not square, the Netpbm output image has the
       wrong  aspect  ratio.   In  this case, giftopnm issues an informational
       message telling you to run pnmscale to correct the output.

OPTIONS
       --alphaout=alpha-filename
              giftopnm creates a PGM (portable graymap)  file  containing  the
              alpha  channel  values  in  the input image.  If the input image
              doesn't contain an alpha channel, the alpha-filename  file  con-
              tains all zero (transparent) alpha values.  If you don't specify
              --alphaout, giftopnm does not generate an alpha file, and if the
              input image has an alpha channel, giftopnm simply discards it.

              If you specify - as the filename, giftopnm writes the alpha out-
              put to Standard Output and discards the image.

              See pnmcomp(1) for one way to use the alpha output file.

       -verbose
              Produce verbose output about the GIF file input.

       -comments
              Only output GIF89 comment fields.

       -image N
              Output the specified gif image from the input GIF archive (where
              N  is  '1', '2', '20'...).  Normally there is only one image per
              file, so this option is not needed.

       All flags can be abbreviated to their shortest unique prefix.

RESTRICTIONS
       This does not correctly handle the Plain Text Extension  of  the  GIF89
       standard, since I did not have any example input files containing them.

SEE ALSO
       ppmtogif(1),       ppmcolormask(1),       pnmcomp(1),       gifsicle(1)
       <http://www.lcdf.org/gifsicle>, ppm(5).

AUTHOR
       Copyright (c) 1993 by David Koblas (koblas@netcom.com)

LICENSE
       If you use giftopnm, 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  li-
       cense  for  trivial  use  of the patent.  Unisys has never enforced the
       patent against trivial users, and has made statements that it  is  much
       less  concerned  about people using the patent for decompression (which
       is what giftopnm does than for compression.  The patent expires in 2003
       / 2004, depending on the country.

       Rumor has it that IBM also owns a patent covering giftopnm.

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

                                13 January 2001                    giftopnm(1)