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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