File Source for PelJpeg.php

<?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, 2006, 2007 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 representing JPEG 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('PelJpegComment.php');
require_once('PelJpegContent.php');
require_once('PelDataWindow.php');
require_once('PelJpegMarker.php');
require_once('PelException.php');
require_once('PelExif.php');
require_once('Pel.php');
/**#@-*/
/**
* Exception thrown when an invalid marker is found.
*
* This exception is thrown when PEL expects to find a {@link }
* PelJpegMarker} and instead finds a byte that isn't a known marker.
*
* @author Martin Geisler <mgeisler@users.sourceforge.net>
* @package PEL
* @subpackage Exception
*/
class PelJpegInvalidMarkerException extends PelException {
/**
* Construct a new invalid marker exception.
*
* The exception will contain a message describing the error,
* including the byte found and the offset of the offending byte.
*
* @param int the byte found.
*
* @param int the offset in the data.
*/
function __construct($marker, $offset) {
parent::__construct('Invalid marker found at offset %d: 0x%2X',
$offset, $marker);
}
}
/**
* Class for handling JPEG data.
*
* The {@link PelJpeg} class defined here provides an abstraction for
* dealing with a JPEG file. The file will be contain a number of
* sections containing some {@link PelJpegContent content} identified
* by a {@link PelJpegMarker marker}.
*
* The {@link getExif()} method is used get hold of the {@link }
* PelJpegMarker::APP1 APP1} section which stores Exif data. So if
* the name of the JPEG file is stored in $filename, then one would
* get hold of the Exif data by saying:
*
* <code>
* $jpeg = new PelJpeg($filename);
* $exif = $jpeg->getExif();
* $tiff = $exif->getTiff();
* $ifd0 = $tiff->getIfd();
* $exif = $ifd0->getSubIfd(PelIfd::EXIF);
* $ifd1 = $ifd0->getNextIfd();
* </code>
*
* The $idf0 and $ifd1 variables will then be two {@link PelTiff TIFF}
* {@link PelIfd Image File Directories}, in which the data is stored
* under the keys found in {@link PelTag}.
*
* Should one have some image data (in the form of a {@link }
* PelDataWindow}) of an unknown type, then the {@link }
* PelJpeg::isValid()} function is handy: it will quickly test if the
* data could be valid JPEG data. The {@link PelTiff::isValid()}
* function does the same for TIFF images.
*
* @author Martin Geisler <mgeisler@users.sourceforge.net>
* @package PEL
*/
class PelJpeg {
/**
* The sections in the JPEG data.
*
* A JPEG file is built up as a sequence of sections, each section
* is identified with a {@link PelJpegMarker}. Some sections can
* occur more than once in the JPEG stream (the {@link }
* PelJpegMarker::DQT DQT} and {@link PelJpegMarker::DHT DTH}
* markers for example) and so this is an array of ({@link }
* PelJpegMarker}, {@link PelJpegContent}) pairs.
*
* The content can be either generic {@link PelJpegContent JPEG}
* content} or {@link PelExif Exif data}.
*
* @var array
*/
private $sections = array();
/**
* The JPEG image data.
*
* @var PelDataWindow
*/
private $jpeg_data = null;
/**
* Construct a new JPEG object.
*
* The new object will be empty unless an argument is given from
* which it can initialize itself. This can either be the filename
* of a JPEG image, a {@link PelDataWindow} object or a PHP image
* resource handle.
*
* New Exif data (in the form of a {@link PelExif} object) can be
* inserted with the {@link setExif()} method:
*
* <code>
* $jpeg = new PelJpeg($data);
* // Create container for the Exif information:
* $exif = new PelExif();
* // Now Add a PelTiff object with a PelIfd object with one or more
* // PelEntry objects to $exif... Finally add $exif to $jpeg:
* $jpeg->setExif($exif);
* </code>
*
* @param mixed the data that this JPEG. This can either be a
* filename, a {@link PelDataWindow} object, or a PHP image resource
* handle.
*/
function __construct($data = false) {
if ($data === false)
return;
if (is_string($data)) {
Pel::debug('Initializing PelJpeg object from %s', $data);
$this->loadFile($data);
} elseif ($data instanceof PelDataWindow) {
Pel::debug('Initializing PelJpeg object from PelDataWindow.');
$this->load($data);
} elseif (is_resource($data) && get_resource_type($data) == 'gd') {
Pel::debug('Initializing PelJpeg object from image resource.');
$this->load(new PelDataWindow($data));
} else {
throw new PelInvalidArgumentException('Bad type for $data: %s',
gettype($data));
}
}
/**
* Load data into a JPEG object.
*
* The data supplied will be parsed and turned into an object
* structure representing the image. This structure can then be
* manipulated and later turned back into an string of bytes.
*
* This methods can be called at any time after a JPEG object has
* been constructed, also after the {@link appendSection()} has been
* called to append custom sections. Loading several JPEG images
* into one object will accumulate the sections, but there will only
* be one {@link PelJpegMarker::SOS} section at any given time.
*
* @param PelDataWindow the data that will be turned into JPEG
* sections.
*/
function load(PelDataWindow $d) {
Pel::debug('Parsing %d bytes...', $d->getSize());
/* JPEG data is stored in big-endian format. */
$d->setByteOrder(PelConvert::BIG_ENDIAN);
/* Run through the data to read the sections in the image. After
* each section is read, the start of the data window will be
* moved forward, and after the last section we'll terminate with
* no data left in the window. */
while ($d->getSize() > 0) {
/* JPEG sections start with 0xFF. The first byte that is not
* 0xFF is a marker (hopefully).
*/
for ($i = 0; $i < 7; $i++)
if ($d->getByte($i) != 0xFF)
break;
$marker = $d->getByte($i);
if (!PelJpegMarker::isValid($marker))
throw new PelJpegInvalidMarkerException($marker, $i);
/* Move window so first byte becomes first byte in this
* section. */
$d->setWindowStart($i+1);
if ($marker == PelJpegMarker::SOI || $marker == PelJpegMarker::EOI) {
$content = new PelJpegContent(new PelDataWindow());
$this->appendSection($marker, $content);
} else {
/* Read the length of the section. The length includes the
* two bytes used to store the length. */
$len = $d->getShort(0) - 2;
Pel::debug('Found %s section of length %d',
PelJpegMarker::getName($marker), $len);
/* Skip past the length. */
$d->setWindowStart(2);
if ($marker == PelJpegMarker::APP1) {
try {
$content = new PelExif();
$content->load($d->getClone(0, $len));
} catch (PelInvalidDataException $e) {
/* We store the data as normal JPEG content if it could
* not be parsed as Exif data. */
$content = new PelJpegContent($d->getClone(0, $len));
}
$this->appendSection($marker, $content);
/* Skip past the data. */
$d->setWindowStart($len);
} elseif ($marker == PelJpegMarker::COM) {
$content = new PelJpegComment();
$content->load($d->getClone(0, $len));
$this->appendSection($marker, $content);
$d->setWindowStart($len);
} else {
$content = new PelJpegContent($d->getClone(0, $len));
$this->appendSection($marker, $content);
/* Skip past the data. */
$d->setWindowStart($len);
/* In case of SOS, image data will follow. */
if ($marker == PelJpegMarker::SOS) {
/* Some images have some trailing (garbage?) following the
* EOI marker. To handle this we seek backwards until we
* find the EOI marker. Any trailing content is stored as
* a PelJpegContent object. */
$length = $d->getSize();
while ($d->getByte($length-2) != 0xFF ||
$d->getByte($length-1) != PelJpegMarker::EOI) {
$length--;
}
$this->jpeg_data = $d->getClone(0, $length-2);
Pel::debug('JPEG data: ' . $this->jpeg_data->__toString());
/* Append the EOI. */
$this->appendSection(PelJpegMarker::EOI,
new PelJpegContent(new PelDataWindow()));
/* Now check to see if there are any trailing data. */
if ($length != $d->getSize()) {
Pel::maybeThrow(new PelException('Found trailing content ' .
'after EOI: %d bytes',
$d->getSize() - $length));
$content = new PelJpegContent($d->getClone($length));
/* We don't have a proper JPEG marker for trailing
* garbage, so we just use 0x00... */
$this->appendSection(0x00, $content);
}
/* Done with the loop. */
break;
}
}
}
} /* while ($d->getSize() > 0) */
}
/**
* Load data from a file into a JPEG object.
*
* @param string the filename. This must be a readable file.
*/
function loadFile($filename) {
$this->load(new PelDataWindow(file_get_contents($filename)));
}
/**
* Set Exif data.
*
* Use this to set the Exif data in the image. This will overwrite
* any old Exif information in the image.
*
* @param PelExif the Exif data.
*/
function setExif(PelExif $exif) {
$app0_offset = 1;
$app1_offset = -1;
/* Search through all sections looking for APP0 or APP1. */
for ($i = 0; $i < count($this->sections); $i++) {
if ($this->sections[$i][0] == PelJpegMarker::APP0) {
$app0_offset = $i;
} elseif ($this->sections[$i][0] == PelJpegMarker::APP1) {
$app1_offset = $i;
break;
}
}
/* Store the Exif data at the appropriate place, either where the
* old Exif data was stored ($app1_offset) or right after APP0
* ($app0_offset+1). */
if ($app1_offset > 0)
$this->sections[$app1_offset][1] = $exif;
else
$this->insertSection(PelJpegMarker::APP1, $exif, $app0_offset+1);
}
/**
* Get Exif data.
*
* Use this to get the @{link PelExif Exif data} stored.
*
* @return PelExif the Exif data found or null if the image has no
* Exif data.
*/
function getExif() {
$exif = $this->getSection(PelJpegMarker::APP1);
if ($exif instanceof PelExif)
return $exif;
else
return null;
}
/**
* Clear any Exif data.
*
* This method will only clear the first @{link PelJpegMarker::APP1}
* section found (there should normally be just one).
*/
function clearExif() {
for ($i = 0; $i < count($this->sections); $i++) {
if ($this->sections[$i][0] == PelJpegMarker::APP1) {
unset($this->sections[$i]);
return;
}
}
}
/**
* Append a new section.
*
* Used only when loading an image. If it used again later, then the
* section will end up after the @{link PelJpegMarker::EOI EOI
* marker} and will probably not be useful.
*
* Please use @{link setExif()} instead if you intend to add Exif
* information to an image as that function will know the right
* place to insert the data.
*
* @param PelJpegMarker the marker identifying the new section.
*
* @param PelJpegContent the content of the new section.
*/
function appendSection($marker, PelJpegContent $content) {
$this->sections[] = array($marker, $content);
}
/**
* Insert a new section.
*
* Please use @{link setExif()} instead if you intend to add Exif
* information to an image as that function will know the right
* place to insert the data.
*
* @param PelJpegMarker the marker for the new section.
*
* @param PelJpegContent the content of the new section.
*
* @param int the offset where the new section will be inserted ---
* use 0 to insert it at the very beginning, use 1 to insert it
* between sections 1 and 2, etc.
*/
function insertSection($marker, PelJpegContent $content, $offset) {
array_splice($this->sections, $offset, 0, array(array($marker, $content)));
}
/**
* Get a section corresponding to a particular marker.
*
* Please use the {@link getExif()} if you just need the Exif data.
*
* This will search through the sections of this JPEG object,
* looking for a section identified with the specified {@link }
* PelJpegMarker marker}. The {@link PelJpegContent content} will
* then be returned. The optional argument can be used to skip over
* some of the sections. So if one is looking for the, say, third
* {@link PelJpegMarker::DHT DHT} section one would do:
*
* <code>
* $dht3 = $jpeg->getSection(PelJpegMarker::DHT, 2);
* </code>
*
* @param PelJpegMarker the marker identifying the section.
*
* @param int the number of sections to be skipped. This must be a
* non-negative integer.
*
* @return PelJpegContent the content found, or null if there is no
* content available.
*/
function getSection($marker, $skip = 0) {
foreach ($this->sections as $s) {
if ($s[0] == $marker)
if ($skip > 0)
$skip--;
else
return $s[1];
}
return null;
}
/**
* Get all sections.
*
* @return array an array of ({@link PelJpegMarker}, {@link }
* PelJpegContent}) pairs. Each pair is an array with the {@link }
* PelJpegMarker} as the first element and the {@link }
* PelJpegContent} as the second element, so the return type is an
* array of arrays.
*
* So to loop through all the sections in a given JPEG image do
* this:
*
* <code>
* foreach ($jpeg->getSections() as $section) {
* $marker = $section[0];
* $content = $section[1];
* // Use $marker and $content here.
* }
* </code>
*
* instead of this:
*
* <code>
* foreach ($jpeg->getSections() as $marker => $content) {
* // Does not work the way you would think...
* }
* </code>
*
* The problem is that there could be several sections with the same
* marker, and thus a simple associative array does not suffice.
*/
function getSections() {
return $this->sections;
}
/**
* Turn this JPEG object into bytes.
*
* The bytes returned by this method is ready to be stored in a file
* as a valid JPEG image. Use the {@link saveFile()} convenience
* method to do this.
*
* @return string bytes representing this JPEG object, including all
* its sections and their associated data.
*/
function getBytes() {
$bytes = '';
foreach ($this->sections as $section) {
$m = $section[0];
$c = $section[1];
/* Write the marker */
$bytes .= "\xFF" . PelJpegMarker::getBytes($m);
/* Skip over empty markers. */
if ($m == PelJpegMarker::SOI || $m == PelJpegMarker::EOI)
continue;
$data = $c->getBytes();
$size = strlen($data) + 2;
$bytes .= PelConvert::shortToBytes($size, PelConvert::BIG_ENDIAN);
$bytes .= $data;
/* In case of SOS, we need to write the JPEG data. */
if ($m == PelJpegMarker::SOS)
$bytes .= $this->jpeg_data->getBytes();
}
return $bytes;
}
/**
* Save the JPEG object as a JPEG image in a file.
*
* @param string the filename to save in. An existing file with the
* same name will be overwritten!
*/
function saveFile($filename) {
file_put_contents($filename, $this->getBytes());
}
/**
* Make a string representation of this JPEG object.
*
* This is mainly usefull for debugging. It will show the structure
* of the image, and its sections.
*
* @return string debugging information about this JPEG object.
*/
function __toString() {
$str = Pel::tra("Dumping JPEG data...\n");
for ($i = 0; $i < count($this->sections); $i++) {
$m = $this->sections[$i][0];
$c = $this->sections[$i][1];
$str .= Pel::fmt("Section %d (marker 0x%02X - %s):\n",
$i, $m, PelJpegMarker::getName($m));
$str .= Pel::fmt(" Description: %s\n",
PelJpegMarker::getDescription($m));
if ($m == PelJpegMarker::SOI ||
$m == PelJpegMarker::EOI)
continue;
if ($c instanceof PelExif) {
$str .= Pel::tra(" Content : Exif data\n");
$str .= $c->__toString() . "\n";
} elseif ($c instanceof PelJpegComment) {
$str .= Pel::fmt(" Content : %s\n", $c->getValue());
} else {
$str .= Pel::tra(" Content : Unknown\n");
}
}
return $str;
}
/**
* Test data to see if it could be a valid JPEG image.
*
* The function will only look at the first few bytes of the data,
* and try to determine if it could be a valid JPEG image based on
* those bytes. This means that the check is more like a heuristic
* than a rigorous check.
*
* @param PelDataWindow the bytes that will be checked.
*
* @return boolean true if the bytes look like the beginning of a
* JPEG image, false otherwise.
*
* @see PelTiff::isValid()
*/
static function isValid(PelDataWindow $d) {
/* JPEG data is stored in big-endian format. */
$d->setByteOrder(PelConvert::BIG_ENDIAN);
for ($i = 0; $i < 7; $i++)
if ($d->getByte($i) != 0xFF)
break;
return $d->getByte($i) == PelJpegMarker::SOI;
}
}
?>

Documentation generated on Thu, 05 May 2011 07:19:18 +0200 by phpDocumentor 1.4.3

Source for file PelJpeg.php