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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 con‐
       tains other colors, the output 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 oth‐
       erwise, 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-file‐
              name file contains all zero (transparent) alpha values.  If you  don't  specify  --al‐‐
              phaout,  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 output 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 AT 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  typi‐
       cally  asks $5000 for a license 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)