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https://github.com/openharmony/third_party_giflib.git
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mamingshuai
222 lines
6.8 KiB
XML
222 lines
6.8 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE article PUBLIC
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"-//OASIS//DTD DocBook XML V4.1.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" [
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<!ENTITY homepage "http://catb.org/~esr/">
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<!ENTITY email "esr@thyrsus.com">
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]>
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<article><title>Introduction to GIFLIB</title>
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<articleinfo>
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<author>
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<firstname>Eric</firstname>
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<othername>Steven</othername>
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<surname>Raymond</surname>
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<affiliation>
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<orgname><ulink url="&homepage;">
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Thyrsus Enterprises</ulink></orgname>
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<address>
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<email>&email;</email>
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</address>
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</affiliation>
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</author>
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<copyright>
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<year>2012</year>
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<holder role="mailto:&email;">Eric S. Raymond</holder>
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</copyright>
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</articleinfo>
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<para>GIFLIB is a package of portable tools and library routines for
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working with GIF images.</para>
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<para>The Graphics Interchange Format(c) specification is the copyrighted
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property of CompuServe Incorporated. GIF(sm) is a service mark
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property of CompuServe Incorporated.</para>
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<para>This package has been released under an X Consortium-like open-source
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license. Use and copy as you see fit. If you make useful changes,
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add new tools, or find and fix bugs, please send your mods to the
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maintainers for general distribution.</para>
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<para>The util directory includes programs to clip, rotate, scale, and
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position GIF images. These are no replacement for an interactive graphics
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editor, but they can be very useful for scripted image generation or
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transformation.</para>
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<para>The library includes program-callable entry points for reading and writing
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GIF files, an 8x8 utility font for embedding text in GIFs, and an error
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handler. GIF manipulation can be done at a relatively low level by
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sequential I/O (which automatically does/undoes image compression) or at
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a higher level by slurping an entire GIF into allocated core.</para>
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<para>This library speaks both GIF87a and GIF89. The differences
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between GIF87 and GIF89 are minor: in the latter, the interpretation
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of some extension block types is defined. The library never needs to
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actually interpret these, but <ulink
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url="giftext.html">giftext</ulink> notices them and there are
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functions in the API to read and modify them.</para>
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<sect1><title>Utilities</title>
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<para>Here is a summary of the utilities in this package. If you're looking
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at this page through a web browser, each utility name should be a
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hotlink to HTML documentation.</para>
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<para>Most utilities have a -v (verbose) option that will cause them to print
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the current input scan line number (counting up) whenever they read
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image input, and will print output image line number (counting down)
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when they dump output. Utilities that only read or write always print
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in increasing order.</para>
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<!--
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Note: the giflib.1 man page is deliberately omitted from the following
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list of references. It's meant to be seen through man(1) only as part
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of a local installation of the tools.
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-->
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<sect2><title>Conversion Utilities</title>
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<variablelist>
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<varlistentry>
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<term><ulink url="gif2rgb.html">gif2rgb</ulink></term>
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<listitem>
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<para>convert images saved as GIF to 24-bit RGB image(s) or vice-versa</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2><title>Test Pattern Generators</title>
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<variablelist>
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<varlistentry>
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<term><ulink url="gifbg.html">gifbg</ulink></term>
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<listitem>
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<para>generate a single-color test pattern GIF</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="gifcolor.html">gifcolor</ulink></term>
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<listitem>
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<para>generate color test patterns</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="gifwedge.html">gifwedge</ulink></term>
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<listitem>
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<para>create a test GIF image resembling a color monitor test pattern</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2><title>Image Manipulation Components</title>
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<variablelist>
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<varlistentry>
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<term><ulink url="gifclrmp.html">gifclrmp</ulink></term>
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<listitem>
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<para>modify GIF image colormaps</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="giffix.html">giffix</ulink></term>
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<listitem>
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<para>clumsily attempts to fix truncated GIF images</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2><title>Report Generators</title>
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<variablelist>
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<varlistentry>
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<term><ulink url="giftext.html">giftext</ulink></term>
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<listitem>
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<para>print (text only) general information about a GIF</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="gifhisto.html">gifhisto</ulink></term>
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<listitem>
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<para>generate color-frequency histogram from a GIF</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2><title>GIF Composition Tools</title>
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<variablelist>
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<varlistentry>
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<term><ulink url="gifbuild.html">gifbuild</ulink></term>
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<listitem>
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<para>converter/deconverter to/from an editable text format</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="gifecho.html">gifecho</ulink></term>
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<listitem>
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<para>generate GIF images out of regular text in 8x8 font</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="gifinto.html">gifinto</ulink></term>
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<listitem>
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<para>end-of-pipe fitting for GIF-processing pipelines</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><ulink url="giftool.html">giftool</ulink></term>
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<listitem>
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<para>GIF transformation tool</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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</sect1>
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<sect1><title>Library Functions</title>
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<para>The library contains two groups of C functions. One group does
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sequential I/O on the stream-oriented GIF format. The other supports
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grabbing an entire GIF into allocated core, operating on it in core,
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and then writing the modified in-core GIF out to disk.</para>
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<para>Unless you are on extremely memory-limited machine, you probably want
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to use the second group.</para>
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<para>Detailed documentation on the library entry points is in <ulink
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url="gif_lib.html">gif_lib.html</ulink>.</para>
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</sect1>
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<sect1><title>The GIF Standard</title>
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<para>The doc subdirectory includes an <ulink
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url="gifstandard/GIF89a.html">HTML presentation of the GIF
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standard</ulink>; an <ulink url="gifstandard/
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LZW-and-GIF-explained.html">explanation of Lempel-Ziv
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compression</ulink>, and the original flat-ASCII description of <ulink
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url="gifstandard/gif89.txt">GIF89 format</ulink> . For historical
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completeness, we also include a copy of the <ulink
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url="gifstandard/gif87.txt">GIF87 standard.</ulink></para>
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<para>You can also read a <ulink url="whatsinagif/index.html">
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detailed narrative description</ulink> of how GIFs are laid out. It
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clarifies some points on which the standard is obscure.</para>
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</sect1>
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<sect1><title>Package Status</title>
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<para>GIFLIB's current maintainer is Eric S. Raymond. You can find his home
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page at <ulink url="&homepage;">&homepage;</ulink>.</para>
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<para>GIFLIB is not under active development, but bug fixes are being
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accepted.</para>
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</sect1>
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</article>
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