<?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;
    }

}

