1GIFSICLE 1.21
2=============
3
4ABOUT GIFSICLE
5--------------
6 Gifsicle twaddles GIF image files in a variety of ways. It is better
7than many of the freely available GIF twaddlers on the market -- for one
8thing, it has more options.
9
10 It supports merging several GIFs into a GIF animation; exploding an
11animation into its component frames; changing individual frames in an
12animation; turning interlacing on and off; adding transparency; adding
13delays, disposals, and looping to animations; adding or removing comments;
14flipping and rotation; optimizing animations for space; and changing
15images' colormaps, among other things. Extensive command-line options
16control which, if any, of these occur.
17
18 Gifview, a companion program requiring X11, displays GIF images and
19animations on an X display. It can display multi-frame GIFs either as
20slideshows, displaying one frame at a time, or as real-time animations.
21
22 Gifdiff, another companion program, checks two GIF files for identical
23visual appearance. This is probably most useful for testing
24GIF-manipulating software.
25
26 Each of these programs has a manpage, `PROGRAMNAME.1'.
27
28 The Gifsicle package comes with NO WARRANTY, express or implied,
29including, but not limited to, the implied warranties of merchantability
30and fitness for a particular purpose.
31
32THE GIF PATENTS AND UNGIFS
33--------------------------
34 Unisys owns patents on the Lempel-Ziv-Welch compression algorithm used
35in GIFs, which means that GIF-manipulating software cannot be truly free.
36Some people in the know have said that decompression is not covered by the
37LZW patents (I have my doubts). That leaves compression. Independently,
38Toshio Kuratomi <badger@prtr-13.ucsc.edu> and Hutchison Avenue Software
39Corporation (http://www.hasc.com/, <info@hasc.com>) cut the Gordian knot by
40writing GIFs without LZW compression. These GIFs are larger, but perfectly
41readable by normal GIF viewers, and they avoid the Unisys patents.
42
43 Gifsicle can be configured to write run-length-encoded GIFs, rather than
44LZW-compressed GIFs, making it completely free software (if you believe
45that decompression isn't patented). Turn this on by giving `./configure'
46the `--enable-ungif' switch. The disadvantage: your GIF outputs will be
47larger, often by a factor of 2 or more. You can tell which gifsicle you are
48running by typing `gifsicle --version'. If it says `(ungif)', gifsicle is
49writing run-length-encoded GIFs.
50
51 This gifsicle package may have been distributed without the file that
52implements LZW compression. If you try to configure such a distribution
53without `--enable-ungif', you will get an error message. See the Gifsicle
54web page <http://www.lcdf.org/gifsicle/> if you have such a distribution
55but want LZW compression.
56
57MAKING GIFSICLE ON UNIX
58-----------------------
59 You need an ANSI C compiler, such as gcc.
60
61 Just type `./configure', then `make'. `make install' will build and
62install gifsicle and its manual page (under /usr/local by default).
63
64 `./configure' accepts the usual options. See `INSTALL' for more
65details.
66
67 To build without gifview (for example, if you don't have X11), give the
68`--disable-gifview' option. To build without gifdiff, give the
69`--disable-gifdiff' option. To have Gifsicle create unGIFs instead of GIFs,
70avoiding the Unisys patents, give the `--enable-ungif' option.
71
72MAKING GIFSICLE ON 32-BIT WINDOWS
73---------------------------------
74 Emil Mikulic <darkmoon@connexus.net.au> has provided a Makefile for
75building gifsicle out of the box on 32-bit Windows. It has since been
76updated by Eddie Kohler and Steven Marthouse <comments@vrml3d.com>. Just
77unpack the distribution, change into that directory, and type
78
79 nmake -f Makefile.w32
80
81Gifview will not be built. You will need to edit `Makefile.w32' if you are
82building ungifsicle, or if you are not compiling with a Microsoft compiler.
83You can edit it with any text editor (like Notepad). See the file for more
84information.
85
86CHANGES
87-------
88 See `NEWS' in this directory for a detailed listing of changes.
89
90BUGS, SUGGESTIONS, ETC.
91-----------------------
92 Please write me if you have trouble building or running gifsicle, or if
93you have suggestions or patches.
94
95 Eddie Kohler
96 eddietwo@lcs.mit.edu
97 http://www.pdos.lcs.mit.edu/~eddietwo/
98
99GIFSICLE HOME PAGE
100------------------
101 For latest distributions, bug reports, and other stuff, see the Gifsicle
102home page at
103
104 http://www.lcdf.org/gifsicle/
105
106COPYRIGHT/LICENSE
107-----------------
108 All source code is Copyright (C) 1997-9 Eddie Kohler.
109
110 IF YOU PLAN TO USE GIFSICLE ONLY TO CREATE OR MODIFY GIF IMAGES, DON'T
111WORRY ABOUT THE REST OF THIS SECTION. Anyone can use Gifsicle however they
112wish; the license applies only to those who plan to copy, distribute, or
113alter its code. If you use Gifsicle for an organizational or commercial Web
114site, I would appreciate a link to the Gifsicle home page on any `About
115This Server' page, but it's not required.
116
117 This code, with the exception of the GIF compression code in gifwrite.c,
118is distributed under the GNU General Public License, Version 2, or, at your
119discretion, any later version. The GNU General Public License is available
120via the Web at <http://www.gnu.org/copyleft/gpl.html>
121
122 The following alternative license may be used at your discretion.
123
124 Permission is granted to copy, distribute, or alter gifsicle, whole
125or in part, as long as source code copyright notices are kept intact, with
126the following restrictions.
127
128 1. Unisys Corp. holds a patent on the Lempel-Ziv-Welch compression
129algorithm used by GIF images. When this first became an issue several years
130ago, Unisys stated that programs available at no cost to the user, like
131Gifsicle, could use LZW compression in the context of GIF images without
132obtaining a license. If you plan to distribute GIF writing code in a
133shareware or commercial product, you will need to worry about obtaining a
134license. (Many people believe that LZW decompression is not covered by the
135Unisys patent, so GIF reading code is probably all right.)
136
137 2. Developers or distributors who plan to use Gifsicle code, whole or in
138part, in a product whose source code will not be made available to the end
139user -- more precisely, in a context which would violate the GPL -- MUST
140contact the author and obtain permission before doing so.
141
142AUTHORS
143-------
144Eddie Kohler <eddietwo@lcs.mit.edu>
145http://www.pdos.lcs.mit.edu/~eddietwo/
146He wrote it.
147
148Anne Dudfield <anne@lvld.hp.com>
149http://www.frii.com/~annied/
150She named it.
151
152David Hedbor <david@hedbor.org>
153Many bug reports and constructive whining about the optimizer.
154
155Emil Mikulic <darkmoon@connexus.net.au>
156Win32 port help.
157
158Hans Dinsen-Hansen <dino@danbbs.dk>
159http://www.danbbs.dk/~dino/
160Adaptive tree method for GIF writing.
161