giftopnm - convert a GIF file into a portable anymap


SYNOPSIS

       giftopnm [--alphaout={alpha-filename,-}] [-verbose] [-com­
       ments] [-image N] [GIFfile]


DESCRIPTION

       Reads a GIF file for input, and outputs portable anymap.

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

       If the image identifies  a  transparent  background  color
       (i.e.  a  color  that  a user of the image should treat as
       transparent in the event that the image is  overlaid  over
       another), giftopnm issues a message telling you what color
       that is when you use the -verbose option.   You  can  then
       use  ppmcolormask  to  create  a  PGM  file representing a
       transparency mask and use that PGM file with other  Netpbm
       programs to effect transparency.


OPTIONS

       --alphaout=alpha-filename
              giftopnm creates a PGM (portable graymap) file con­
              taining the  alpha  channel  values  in  the  input
              image.  If the input image doesn't contain an alpha
              channel, the alpha-filename file contains 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  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 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.

       fix.


BUGS

       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 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
       giftopnm.

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


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