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<?php
/**
* PEL: PHP Exif Library. A library with support for reading and
* writing all Exif headers in JPEG and TIFF images using PHP.
*
* Copyright (C) 2004, 2005 Martin Geisler.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program in the file COPYING; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
/* $Id$ */
/**
* Classes for dealing with Exif data.
*
* @author Martin Geisler <mgeisler@users.sourceforge.net>
* @version $Revision$
* @date $Date$
* @license http://www.gnu.org/licenses/gpl.html GNU General Public
* License (GPL)
* @package PEL
*/
/**#@+ Required class definitions. */
require_once('PelJpegContent.php');
require_once('PelException.php');
require_once('PelFormat.php');
require_once('PelEntry.php');
require_once('PelTiff.php');
require_once('PelIfd.php');
require_once('PelTag.php');
require_once('Pel.php');
/**#@-*/
/**
* Class representing Exif data.
*
* Exif data resides as {@link PelJpegContent data} and consists of a
* header followed by a number of {@link PelJpegIfd IFDs}.
*
* The interesting method in this class is {@link getTiff()} which
* will return the {@link PelTiff} object which really holds the data
* which one normally think of when talking about Exif data. This is
* because Exif data is stored as an extension of the TIFF file
* format.
*
* @author Martin Geisler <mgeisler@users.sourceforge.net>
* @package PEL
*/
class PelExif extends PelJpegContent {
/**
* Exif header.
*
* The Exif data must start with these six bytes to be considered
* valid.
*/
const EXIF_HEADER = "Exif\0\0";
/**
* The PelTiff object contained within.
*
* @var PelTiff
*/
private $tiff = null;
/**
* Construct a new Exif object.
*
* The new object will be empty --- use the {@link load()} method to
* load Exif data from a {@link PelDataWindow} object, or use the
* {@link setTiff()} to change the {@link PelTiff} object, which is
* the true holder of the Exif {@link PelEntry entries}.
*/
function __construct() {
}
/**
* Load and parse Exif data.
*
* This will populate the object with Exif data, contained as a
* {@link PelTiff} object. This TIFF object can be accessed with
* the {@link getTiff()} method.
*/
function load(PelDataWindow $d) {
Pel::debug('Parsing %d bytes of Exif data...', $d->getSize());
/* There must be at least 6 bytes for the Exif header. */
if ($d->getSize() < 6)
throw new PelInvalidDataException('Expected at least 6 bytes of Exif ' .
'data, found just %d bytes.',
$d->getSize());
/* Verify the Exif header */
if ($d->strcmp(0, self::EXIF_HEADER)) {
$d->setWindowStart(strlen(self::EXIF_HEADER));
} else {
throw new PelInvalidDataException('Exif header not found.');
}
/* The rest of the data is TIFF data. */
$this->tiff = new PelTiff();
$this->tiff->load($d);
}
/**
* Change the TIFF information.
*
* Exif data is really stored as TIFF data, and this method can be
* used to change this data from one {@link PelTiff} object to
* another.
*
* @param PelTiff the new TIFF object.
*/
function setTiff(PelTiff $tiff) {
$this->tiff = $tiff;
}
/**
* Get the underlying TIFF object.
*
* The actual Exif data is stored in a {@link PelTiff} object, and
* this method provides access to it.
*
* @return PelTiff the TIFF object with the Exif data.
*/
function getTiff() {
return $this->tiff;
}
/**
* Produce bytes for the Exif data.
*
* @return string bytes representing this object.
*/
function getBytes() {
return self::EXIF_HEADER . $this->tiff->getBytes();
}
/**
* Return a string representation of this object.
*
* @return string a string describing this object. This is mostly
* useful for debugging.
*/
function __toString() {
return Pel::tra("Dumping Exif data...\n") .
$this->tiff->__toString();
}
}
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