1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE article PUBLIC 3 "-//OASIS//DTD DocBook XML V4.1.2//EN" 4 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" [ 5<!ENTITY homepage "http://catb.org/~esr/"> 6<!ENTITY email "[email protected]"> 7]> 8<article><title>Introduction to GIFLIB</title> 9 10<articleinfo> 11 12<author> 13 <firstname>Eric</firstname> 14 <othername>Steven</othername> 15 <surname>Raymond</surname> 16 <affiliation> 17 <orgname><ulink url="&homepage;"> 18 Thyrsus Enterprises</ulink></orgname> 19 <address> 20 <email>&email;</email> 21 </address> 22 </affiliation> 23</author> 24<copyright> 25 <year>2012</year> 26 <holder role="mailto:&email;">Eric S. Raymond</holder> 27</copyright> 28 29</articleinfo> 30 31<para>GIFLIB is a package of portable tools and library routines for 32working with GIF images.</para> 33 34<para>The Graphics Interchange Format(c) specification is the copyrighted 35property of CompuServe Incorporated. GIF(sm) is a service mark 36property of CompuServe Incorporated.</para> 37 38<para>This package has been released under an X Consortium-like open-source 39license. Use and copy as you see fit. If you make useful changes, 40add new tools, or find and fix bugs, please send your mods to the 41maintainers for general distribution.</para> 42 43<para>The util directory includes programs to clip, rotate, scale, and 44position GIF images. These are no replacement for an interactive graphics 45editor, but they can be very useful for scripted image generation or 46transformation.</para> 47 48<para>The library includes program-callable entry points for reading and writing 49GIF files, an 8x8 utility font for embedding text in GIFs, and an error 50handler. GIF manipulation can be done at a relatively low level by 51sequential I/O (which automatically does/undoes image compression) or at 52a higher level by slurping an entire GIF into allocated core.</para> 53 54<para>This library speaks both GIF87a and GIF89. The differences 55between GIF87 and GIF89 are minor: in the latter, the interpretation 56of some extension block types is defined. The library never needs to 57actually interpret these, but <ulink 58url="giftext.html">giftext</ulink> notices them and there are 59functions in the API to read and modify them.</para> 60 61<sect1><title>Utilities</title> 62 63<para>Here is a summary of the utilities in this package. If you're looking 64at this page through a web browser, each utility name should be a 65hotlink to HTML documentation.</para> 66 67<para>Most utilities have a -v (verbose) option that will cause them to print 68the current input scan line number (counting up) whenever they read 69image input, and will print output image line number (counting down) 70when they dump output. Utilities that only read or write always print 71in increasing order.</para> 72 73<!-- 74Note: the giflib.1 man page is deliberately omitted from the following 75list of references. It's meant to be seen through man(1) only as part 76of a local installation of the tools. 77--> 78 79<sect2><title>Conversion Utilities</title> 80 81<variablelist> 82<varlistentry> 83<term><ulink url="gif2rgb.html">gif2rgb</ulink></term> 84<listitem> 85<para>convert images saved as GIF to 24-bit RGB image(s) or vice-versa</para> 86</listitem> 87</varlistentry> 88</variablelist> 89 90</sect2> 91<sect2><title>Image Manipulation Components</title> 92 93<variablelist> 94<varlistentry> 95<term><ulink url="gifclrmp.html">gifclrmp</ulink></term> 96<listitem> 97<para>modify GIF image colormaps</para> 98</listitem> 99</varlistentry> 100<varlistentry> 101<term><ulink url="giffix.html">giffix</ulink></term> 102<listitem> 103<para>clumsily attempts to fix truncated GIF images</para> 104</listitem> 105</varlistentry> 106</variablelist> 107 108</sect2> 109<sect2><title>Report Generators</title> 110 111<variablelist> 112<varlistentry> 113<term><ulink url="giftext.html">giftext</ulink></term> 114<listitem> 115<para>print (text only) general information about a GIF</para> 116</listitem> 117</varlistentry> 118</variablelist> 119 120</sect2> 121<sect2><title>GIF Composition Tools</title> 122 123<variablelist> 124<varlistentry> 125<term><ulink url="gifbuild.html">gifbuild</ulink></term> 126<listitem> 127<para>converter/deconverter to/from an editable text format</para> 128</listitem> 129</varlistentry> 130<varlistentry> 131<term><ulink url="giftool.html">giftool</ulink></term> 132<listitem> 133<para>GIF transformation tool</para> 134</listitem> 135</varlistentry> 136</variablelist> 137 138</sect2> 139<sect2><title>Obsolete utilities</title> 140 141<para>These are used for testing by the GFLIB developers and no longer 142installed by a normal build.</para> 143 144<variablelist> 145<varlistentry> 146<term><ulink url="gifbg.html">gifbg</ulink></term> 147<listitem> 148<para>generate a single-color test pattern GIF</para> 149</listitem> 150</varlistentry> 151<varlistentry> 152<term><ulink url="gifcolor.html">gifcolor</ulink></term> 153<listitem> 154<para>generate color test patterns</para> 155</listitem> 156</varlistentry> 157<varlistentry> 158<term><ulink url="gifwedge.html">gifwedge</ulink></term> 159<listitem> 160<para>create a test GIF image resembling a color monitor test pattern</para> 161</listitem> 162</varlistentry> 163<varlistentry> 164<term><ulink url="gifhisto.html">gifhisto</ulink></term> 165<listitem> 166<para>generate color-frequency histogram from a GIF</para> 167</listitem> 168</varlistentry> 169<varlistentry> 170<term><ulink url="gifecho.html">gifecho</ulink></term> 171<listitem> 172<para>generate GIF images out of regular text in 8x8 font</para> 173</listitem> 174</varlistentry> 175<varlistentry> 176<term><ulink url="gifinto.html">gifinto</ulink></term> 177<listitem> 178<para>end-of-pipe fitting for GIF-processing pipelines</para> 179</listitem> 180</varlistentry> 181</variablelist> 182 183 184</sect2> 185</sect1> 186<sect1><title>Library Functions</title> 187 188<para>The library contains two groups of C functions. One group does 189sequential I/O on the stream-oriented GIF format. The other supports 190grabbing an entire GIF into allocated core, operating on it in core, 191and then writing the modified in-core GIF out to disk.</para> 192 193<para>Unless you are on extremely memory-limited machine, you probably want 194to use the second group.</para> 195 196<para>Detailed documentation on the library entry points is in <ulink 197url="gif_lib.html">gif_lib.html</ulink>.</para> 198 199</sect1> 200<sect1><title>The GIF Standard</title> 201 202<para>The doc subdirectory includes an <ulink 203url="gifstandard/GIF89a.html">HTML presentation of the GIF 204standard</ulink>; an <ulink url="gifstandard/ 205LZW-and-GIF-explained.html">explanation of Lempel-Ziv 206compression</ulink>, and the original flat-ASCII description of <ulink 207url="gifstandard/gif89.txt">GIF89 format</ulink> . For historical 208completeness, we also include a copy of the <ulink 209url="gifstandard/gif87.txt">GIF87 standard.</ulink></para> 210 211<para>You can also read a <ulink url="whatsinagif/index.html"> 212detailed narrative description</ulink> of how GIFs are laid out. It 213clarifies some points on which the standard is obscure.</para> 214 215</sect1> 216<sect1><title>Package Status</title> 217 218<para>GIFLIB's current maintainer is Eric S. Raymond. You can find his home 219page at <ulink url="&homepage;">&homepage;</ulink>.</para> 220 221<para>GIFLIB is not under active development, but bug fixes are being 222accepted.</para> 223 224</sect1> 225</article> 226