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<!ENTITY suncopy "Copyright (c) 2004, Sun Microsystems, Inc. All Rights Reserved.">

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<refentry id="rdjpgcom-1">

<refmeta><refentrytitle>rdjpgcom</refentrytitle><manvolnum>1</manvolnum>

<refmiscinfo class="date">26 Mar 2004</refmiscinfo>

<refmiscinfo class="sectdesc">&man1;</refmiscinfo>

<refmiscinfo class="software">&release;</refmiscinfo>

<refmiscinfo class="arch">generic</refmiscinfo>

<refmiscinfo class="copyright">&suncopy;</refmiscinfo>

</refmeta>

<indexterm><primary>rdjpgcom</primary></indexterm><indexterm><primary>display

text comments from a JPEG file</primary></indexterm>

<refnamediv id="rdjpgcom-1-name"><refname>rdjpgcom</refname><refpurpose>display

text comments from a JPEG file</refpurpose></refnamediv>

<refsynopsisdiv id="rdjpgcom-1-synp"><title>&synp-tt;</title>

<cmdsynopsis><command>&cmd;</command><arg choice="opt"><option>verbose</option></arg>

<arg choice="opt"><option role="nodash"><replaceable>filename</replaceable></option></arg>

</cmdsynopsis></refsynopsisdiv>

<refsect1 id="rdjpgcom-1-desc"><title>&desc-tt;</title>

<para><command>&cmd;</command> reads the named JPEG or JFIF file, or the standard

input if no file is named, and displays any text comments found in the file

on the standard output.</para>

<para>The JPEG standard allows "comment" (COM) blocks to occur within a JPEG

file. Although the standard does not actually define the intended function

of COM blocks, they are widely used to hold user-supplied text strings. This

enables you to add annotations, titles, index terms, and so on to your JPEG

files, and later retrieve the COM blocks as text. COM blocks do not interfere

with the image stored in the JPEG file. The maximum size of a COM block is

64K, but you can have many COM blocks in one JPEG file.</para>

</refsect1>

<refsect1 id="rdjpgcom-1-opts"><title>&opts-tt;</title>

<para>The following options are supported:</para>

<variablelist termlength="narrow">

<varlistentry><term><option>verbose</option></term><listitem><para>Causes <command>&cmd;</command>

to also display the JPEG image dimensions.</para>

</listitem></varlistentry>

</variablelist></refsect1>

<refsect1 id="rdjpgcom-1-oper"><title>&oper-tt;</title>

<para>The following operands are supported:</para>

<variablelist termlength="narrow">

<varlistentry><term><option role="nodash"><replaceable>filename</replaceable></option></term>

<listitem><para>The name of the JPEG file that contains text comments.</para>

</listitem></varlistentry>

</variablelist></refsect1>

<refsect1 id="rdjpgcom-1-exde"><title>&exde-tt;</title>

<para><command>&cmd;</command> does not depend on the IJG JPEG library. The <command>&cmd;</command>

source code is intended to illustrate the minimum amount of code required

to parse a JPEG file header correctly. </para>

<para>In <option>verbose</option> mode, <command>&cmd;</command> also attempts

to display the contents of any "APP12" markers as text. Some digital cameras

produce APP12 markers that contain useful textual information. You can also

modify the source code to display other APP<replaceable>n</replaceable>

marker types.</para>

</refsect1>

<refsect1 id="rdjpgcom-1-attr"><title>&attr-tt;</title>

<para>See <olink targetdocent="REFMAN5" localinfo="attributes-5"><citerefentry>

<refentrytitle>attributes</refentrytitle><manvolnum>5</manvolnum></citerefentry></olink>

for descriptions of the following attributes:</para>

<informaltable frame="all">

<tgroup cols="2" colsep="1" rowsep="1"><colspec colname="COLSPEC0" colwidth="1*">

<colspec colname="COLSPEC1" colwidth="1*">

<thead>

<row><entry align="center" valign="middle">ATTRIBUTE TYPE</entry><entry align="center"

valign="middle">ATTRIBUTE VALUE</entry></row>

</thead>

<tbody>

<row><entry><para>Availability</para></entry><entry><para>image/library/libjpeg</para></entry>

</row>

<row><entry colname="COLSPEC0"><para>Interface stability</para></entry><entry

colname="COLSPEC1"><para>Volatile</para></entry></row>

</tbody>

</tgroup>

</informaltable>

</refsect1>

<refsect1 id="rdjpgcom-1-also"><title>&also-tt;</title>

<para><citerefentry><refentrytitle>cjpeg</refentrytitle><manvolnum>1</manvolnum>

</citerefentry>, <citerefentry><refentrytitle>djpeg</refentrytitle><manvolnum>

1</manvolnum></citerefentry>, <citerefentry><refentrytitle>jpegtran</refentrytitle>

<manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>wrjpgcom

</refentrytitle><manvolnum>1</manvolnum></citerefentry></para>

</refsect1>

<refsect1 id="rdjpgcom-1-note"><title>&note-tt;</title>

<para>This man page was originally written by the Independent JPEG Group.

Updated by Breda McColgan, Sun Microsystems Inc., 2004. </para>

</refsect1>

</refentry>