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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@165326 c90b9560-bf6c-de11-be94-00142212c4b1
252 lines
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9 KiB
XML
252 lines
No EOL
9 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.2 $ -->
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<!-- splitted from ./en/functions/image.xml, last change in rev 1.78 -->
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<refentry id="function.exif-read-data">
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<refnamediv>
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<refname>exif_read_data</refname>
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<refpurpose>Reads the <acronym>EXIF</acronym> headers from <acronym>JPEG</acronym>
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or <acronym>TIFF</acronym></refpurpose>
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</refnamediv>
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<refsect1>
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&reftitle.description;
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<methodsynopsis>
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<type>array</type><methodname>exif_read_data</methodname>
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<methodparam><type>string</type><parameter>filename</parameter></methodparam>
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<methodparam choice="opt"><type>string</type><parameter>sections</parameter></methodparam>
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<methodparam choice="opt"><type>bool</type><parameter>arrays</parameter></methodparam>
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<methodparam choice="opt"><type>bool</type><parameter>thumbnail</parameter></methodparam>
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</methodsynopsis>
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<para>
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The <function>exif_read_data</function> function reads the
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<acronym>EXIF</acronym> headers from a <acronym>JPEG</acronym> or
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<acronym>TIFF</acronym> image file. This way you can read meta data
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generated by digital cameras.
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</para>
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<para>
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<parameter>filename</parameter> is the name of the file to read. This
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cannot be a URL.
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</para>
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<para>
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<parameter>sections</parameter> is a comma separated list of sections that
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need to be present in file to produce a result array. If none of the
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requested sections could be found the return value is &false;.
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<informaltable>
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<tgroup cols="2">
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<tbody>
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<row>
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<entry>FILE</entry>
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<entry>FileName, FileSize, FileDateTime, SectionsFound</entry>
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</row>
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<row>
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<entry>COMPUTED</entry>
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<entry>html, Width, Height, IsColor and some more if available.
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</entry>
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</row>
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<row>
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<entry>ANY_TAG</entry>
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<entry>Any information that has a Tag e.g. IFD0, EXIF, ...</entry>
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</row>
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<row>
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<entry>IFD0</entry>
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<entry>All tagged data of IFD0. In normal imagefiles this contains
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image size and so forth.</entry>
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</row>
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<row>
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<entry>THUMBNAIL</entry>
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<entry>A file is supposed to contain a thumbnail if it has a second IFD.
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All tagged information about the embedded thumbnail is stored in this
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section.</entry>
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</row>
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<row>
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<entry>COMMENT</entry>
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<entry>Comment headers of JPEG images.</entry>
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</row>
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<row>
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<entry>EXIF</entry>
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<entry>The EXIF section is a sub section of IFD0. It contains
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more detailed information about an image. Most of these entries
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are digital camera related.</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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<para>
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<parameter>arrays</parameter> specifies whether or not each section
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becomes an array. The sections <emphasis>COMPUTED</emphasis>,
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<emphasis>THUMBNAIL</emphasis> and <emphasis>COMMENT</emphasis> always
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become arrays as they may contain values whose names are conflict
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with other sections.
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</para>
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<para>
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<parameter>thumbnail</parameter> whether or not to read the thumbnail
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itself and not only its tagged data.
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</para>
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<note>
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<para>
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Exif headers tend to be present in JPEG/TIFF images generated by digital
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cameras, but unfortunately each digital camera maker has a different
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idea of how to actually tag their images, so you can't always rely on
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a specific Exif header being present.
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</para>
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<para>
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Windows ME/XP both can wipe the Exif headers when connecting to a camera.
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More information available at <ulink
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url="&url.winexif;">&url.winexif;</ulink>.
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</para>
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</note>
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<note>
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<para>
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If the image contains any IFD0 data then COMPUTED contains the entry
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ByteOrderMotorola which is 0 for little-endian (intel) and 1 for
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big-endian (motorola) byte order. This was added in PHP 4.3.0.
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</para>
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<para>
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When an Exif header contains a Copyright note this itself can contain two
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values. As the solution is inconsistent in the Exif 2.10 standard the COMPUTED
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section will return both entries <emphasis>Copyright.Photographer</emphasis>
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and <emphasis>Copyright.Editor</emphasis> while the IFD0 sections contains
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the byte array with the NULL character that splits both entries. Or just the
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first entry if the datatype was wrong (normal behaviour of Exif). The
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COMPUTED will contain also an entry <emphasis>Copyright</emphasis> Which
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is either the original copyright string or it is a comma separated list of
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photo and editor copyright.
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</para>
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</note>
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<note>
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<para>
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The tag UserComment has the same problem as the Copyright tag. It can store
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two values first the encoding used and second the value itself. If so the
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IFD section only contains the encoding or a byte array. The COMPUTED section
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will store both in the entries <emphasis>UserCommentEncoding</emphasis> and
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<emphasis>UserComment</emphasis>. The entry <emphasis>UserComment</emphasis>
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is available in both cases so it should be used in preference to the value
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in IFD0 section.
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</para>
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<para>
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If the user comment uses Unicode or JIS encoding and the module mbstring is
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available this encoding will automatically changed according to the exif
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ini settings in the &php.ini;. This was added in PHP 4.3.0.
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</para>
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</note>
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<note>
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<para>
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Height and Width are computed the same way <function>getimagesize</function>
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does so their values must not be part of any header returned. Also html is
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a height/width text string to be used inside normal <acronym>HTML</acronym>.
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</para>
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</note>
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<note>
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<para>
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Starting from PHP 4.3.0, the function can read all embedded
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<acronym>IFD</acronym> data including arrays (returned as such). Also
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the size of an embedded thumbnail is returned in
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<emphasis>THUMBNAIL</emphasis> subarray and the function
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<function>exif_read_data</function> can return thumbnails in
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<acronym>TIFF</acronym> format. Also as of PHP 4.3.0 there is no longer
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a maximum length for returned values (not until memory limit is reached).
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</para>
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</note>
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<simpara>
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Since PHP 4.3,0 user comment can automatically change encoding if PHP was
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compiled using <option role="configure">--enable-mbstring</option>.
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</simpara>
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</refsect1>
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<refsect1>
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&reftitle.returnvalues;
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<para>
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It returns an associative <type>array</type> where the array indexes are
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the header names and the array values are the values associated with
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those headers. If no data can be returned,
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<function>exif_read_data</function> will return &false;.
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</para>
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</refsect1>
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<refsect1>
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&reftitle.examples;
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<para>
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<example>
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<title><function>exif_read_data</function> example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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echo "test1.jpg:<br />\n";
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$exif = exif_read_data('tests/test1.jpg', 'IFD0');
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echo $exif===false ? "No header data found.<br />\n" : "Image contains headers<br />";
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$exif = exif_read_data('tests/test2.jpg', 0, true);
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echo "test2.jpg:<br />\n";
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foreach ($exif as $key => $section) {
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foreach ($section as $name => $val) {
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echo "$key.$name: $val<br />\n";
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}
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}
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?>
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]]>
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</programlisting>
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<para>
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The first call fails because the image has no header information.
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</para>
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<screen role="php">
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<![CDATA[
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test1.jpg:
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No header data found.
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test2.jpg:
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FILE.FileName: test2.jpg
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FILE.FileDateTime: 1017666176
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FILE.FileSize: 1240
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FILE.FileType: 2
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FILE.SectionsFound: ANY_TAG, IFD0, THUMBNAIL, COMMENT
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COMPUTED.html: width="1" height="1"
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COMPUTED.Height: 1
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COMPUTED.Width: 1
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COMPUTED.IsColor: 1
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COMPUTED.ByteOrderMotorola: 1
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COMPUTED.UserComment: Exif test image.
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COMPUTED.UserCommentEncoding: ASCII
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COMPUTED.Copyright: Photo (c) M.Boerger, Edited by M.Boerger.
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COMPUTED.Copyright.Photographer: Photo (c) M.Boerger
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COMPUTED.Copyright.Editor: Edited by M.Boerger.
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IFD0.Copyright: Photo (c) M.Boerger
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IFD0.UserComment: ASCII
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THUMBNAIL.JPEGInterchangeFormat: 134
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THUMBNAIL.JPEGInterchangeFormatLength: 523
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COMMENT.0: Comment #1.
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COMMENT.1: Comment #2.
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COMMENT.2: Comment #3end
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THUMBNAIL.JPEGInterchangeFormat: 134
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THUMBNAIL.Thumbnail.Height: 1
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THUMBNAIL.Thumbnail.Height: 1
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]]>
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</screen>
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</example>
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</para>
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</refsect1>
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<refsect1>
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&reftitle.seealso;
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<para>
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<function>exif_thumbnail</function>&listendand;
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<function>getimagesize</function>.
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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--> |