175 lines
4.7 KiB
PHP
175 lines
4.7 KiB
PHP
<?php
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/* PEL: PHP Exif Library. A library with support for reading and
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* writing all Exif headers in JPEG and TIFF images using PHP.
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*
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* Copyright (C) 2004, 2005 Martin Geisler.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program in the file COPYING; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301 USA
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*/
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/* $Id: PelExif.php 380 2005-10-03 12:01:28Z mgeisler $ */
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/**
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* Classes for dealing with Exif data.
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*
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* @author Martin Geisler <mgeisler@users.sourceforge.net>
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* @version $Revision: 380 $
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* @date $Date: 2005-10-03 14:01:28 +0200 (Mon, 03 Oct 2005) $
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* @license http://www.gnu.org/licenses/gpl.html GNU General Public
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* License (GPL)
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* @package PEL
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*/
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/**#@+ Required class definitions. */
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require_once('PelJpegContent.php');
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require_once('PelException.php');
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require_once('PelFormat.php');
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require_once('PelEntry.php');
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require_once('PelTiff.php');
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require_once('PelIfd.php');
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require_once('PelTag.php');
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require_once('Pel.php');
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/**#@-*/
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/**
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* Class representing Exif data.
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*
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* Exif data resides as {@link PelJpegContent data} and consists of a
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* header followed by a number of {@link PelJpegIfd IFDs}.
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*
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* The interesting method in this class is {@link getTiff()} which
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* will return the {@link PelTiff} object which really holds the data
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* which one normally think of when talking about Exif data. This is
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* because Exif data is stored as an extension of the TIFF file
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* format.
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*
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* @author Martin Geisler <mgeisler@users.sourceforge.net>
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* @package PEL
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*/
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class PelExif extends PelJpegContent {
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/**
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* Exif header.
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*
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* The Exif data must start with these six bytes to be considered
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* valid.
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*/
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const EXIF_HEADER = "Exif\0\0";
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/**
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* The PelTiff object contained within.
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*
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* @var PelTiff
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*/
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private $tiff = null;
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/**
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* Construct a new Exif object.
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*
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* The new object will be empty --- use the {@link load()} method to
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* load Exif data from a {@link PelDataWindow} object, or use the
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* {@link setTiff()} to change the {@link PelTiff} object, which is
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* the true holder of the Exif {@link PelEntry entries}.
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*/
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function __construct() {
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}
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/**
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* Load and parse Exif data.
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*
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* This will populate the object with Exif data, contained as a
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* {@link PelTiff} object. This TIFF object can be accessed with
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* the {@link getTiff()} method.
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*/
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function load(PelDataWindow $d) {
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Pel::debug('Parsing %d bytes of Exif data...', $d->getSize());
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/* There must be at least 6 bytes for the Exif header. */
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if ($d->getSize() < 6)
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throw new PelInvalidDataException('Expected at least 6 bytes of Exif ' .
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'data, found just %d bytes.',
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$d->getSize());
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/* Verify the Exif header */
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if ($d->strcmp(0, self::EXIF_HEADER)) {
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$d->setWindowStart(strlen(self::EXIF_HEADER));
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} else {
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throw new PelInvalidDataException('Exif header not found.');
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}
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/* The rest of the data is TIFF data. */
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$this->tiff = new PelTiff();
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$this->tiff->load($d);
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}
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/**
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* Change the TIFF information.
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*
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* Exif data is really stored as TIFF data, and this method can be
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* used to change this data from one {@link PelTiff} object to
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* another.
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*
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* @param PelTiff the new TIFF object.
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*/
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function setTiff(PelTiff $tiff) {
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$this->tiff = $tiff;
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}
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/**
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* Get the underlying TIFF object.
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*
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* The actual Exif data is stored in a {@link PelTiff} object, and
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* this method provides access to it.
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*
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* @return PelTiff the TIFF object with the Exif data.
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*/
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function getTiff() {
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return $this->tiff;
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}
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/**
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* Produce bytes for the Exif data.
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*
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* @return string bytes representing this object.
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*/
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function getBytes() {
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return self::EXIF_HEADER . $this->tiff->getBytes();
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}
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/**
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* Return a string representation of this object.
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*
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* @return string a string describing this object. This is mostly
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* useful for debugging.
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*/
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function __toString() {
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return Pel::tra("Dumping Exif data...\n") .
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$this->tiff->__toString();
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}
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}
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?>
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