5506a8d43d
In theory JPEG files are not allowed to contain anything between the sections, but in practice they sometimes do. It's customary to ignore the garbage data. Bug: T148606 Change-Id: I98f2609644bcd8bfd7c1679afc6e7af83e228685
294 lines
9.7 KiB
PHP
294 lines
9.7 KiB
PHP
<?php
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/**
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* Extraction of JPEG image metadata.
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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 along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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* @ingroup Media
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*/
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/**
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* Class for reading jpegs and extracting metadata.
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* see also BitmapMetadataHandler.
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*
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* Based somewhat on GIFMetadataExtractor.
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*
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* @ingroup Media
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*/
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class JpegMetadataExtractor {
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const MAX_JPEG_SEGMENTS = 200;
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// the max segment is a sanity check.
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// A jpeg file should never even remotely have
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// that many segments. Your average file has about 10.
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/** Function to extract metadata segments of interest from jpeg files
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* based on GIFMetadataExtractor.
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*
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* we can almost use getimagesize to do this
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* but gis doesn't support having multiple app1 segments
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* and those can't extract xmp on files containing both exif and xmp data
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*
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* @param string $filename Name of jpeg file
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* @return array Array of interesting segments.
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* @throws MWException If given invalid file.
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*/
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static function segmentSplitter( $filename ) {
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$showXMP = XMPReader::isSupported();
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$segmentCount = 0;
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$segments = [
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'XMP_ext' => [],
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'COM' => [],
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'PSIR' => [],
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];
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if ( !$filename ) {
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throw new MWException( "No filename specified for " . __METHOD__ );
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}
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if ( !file_exists( $filename ) || is_dir( $filename ) ) {
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throw new MWException( "Invalid file $filename passed to " . __METHOD__ );
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}
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$fh = fopen( $filename, "rb" );
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if ( !$fh ) {
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throw new MWException( "Could not open file $filename" );
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}
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$buffer = fread( $fh, 2 );
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if ( $buffer !== "\xFF\xD8" ) {
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throw new MWException( "Not a jpeg, no SOI" );
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}
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while ( !feof( $fh ) ) {
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$buffer = fread( $fh, 1 );
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$segmentCount++;
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if ( $segmentCount > self::MAX_JPEG_SEGMENTS ) {
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// this is just a sanity check
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throw new MWException( 'Too many jpeg segments. Aborting' );
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}
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while ( $buffer !== "\xFF" ) {
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// In theory JPEG files are not allowed to contain anything between the sections,
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// but in practice they sometimes do. It's customary to ignore the garbage data.
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$buffer = fread( $fh, 1 );
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}
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$buffer = fread( $fh, 1 );
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while ( $buffer === "\xFF" && !feof( $fh ) ) {
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// Skip through any 0xFF padding bytes.
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$buffer = fread( $fh, 1 );
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}
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if ( $buffer === "\xFE" ) {
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// COM section -- file comment
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// First see if valid utf-8,
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// if not try to convert it to windows-1252.
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$com = $oldCom = trim( self::jpegExtractMarker( $fh ) );
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UtfNormal\Validator::quickIsNFCVerify( $com );
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// turns $com to valid utf-8.
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// thus if no change, its utf-8, otherwise its something else.
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if ( $com !== $oldCom ) {
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MediaWiki\suppressWarnings();
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$com = $oldCom = iconv( 'windows-1252', 'UTF-8//IGNORE', $oldCom );
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MediaWiki\restoreWarnings();
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}
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// Try it again, if its still not a valid string, then probably
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// binary junk or some really weird encoding, so don't extract.
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UtfNormal\Validator::quickIsNFCVerify( $com );
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if ( $com === $oldCom ) {
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$segments["COM"][] = $oldCom;
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} else {
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wfDebug( __METHOD__ . " Ignoring JPEG comment as is garbage.\n" );
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}
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} elseif ( $buffer === "\xE1" ) {
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// APP1 section (Exif, XMP, and XMP extended)
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// only extract if XMP is enabled.
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$temp = self::jpegExtractMarker( $fh );
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// check what type of app segment this is.
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if ( substr( $temp, 0, 29 ) === "http://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
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$segments["XMP"] = substr( $temp, 29 );
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} elseif ( substr( $temp, 0, 35 ) === "http://ns.adobe.com/xmp/extension/\x00" && $showXMP ) {
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$segments["XMP_ext"][] = substr( $temp, 35 );
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} elseif ( substr( $temp, 0, 29 ) === "XMP\x00://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
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// Some images (especially flickr images) seem to have this.
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// I really have no idea what the deal is with them, but
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// whatever...
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$segments["XMP"] = substr( $temp, 29 );
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wfDebug( __METHOD__ . ' Found XMP section with wrong app identifier '
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. "Using anyways.\n" );
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} elseif ( substr( $temp, 0, 6 ) === "Exif\0\0" ) {
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// Just need to find out what the byte order is.
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// because php's exif plugin sucks...
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// This is a II for little Endian, MM for big. Not a unicode BOM.
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$byteOrderMarker = substr( $temp, 6, 2 );
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if ( $byteOrderMarker === 'MM' ) {
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$segments['byteOrder'] = 'BE';
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} elseif ( $byteOrderMarker === 'II' ) {
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$segments['byteOrder'] = 'LE';
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} else {
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wfDebug( __METHOD__ . " Invalid byte ordering?!\n" );
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}
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}
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} elseif ( $buffer === "\xED" ) {
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// APP13 - PSIR. IPTC and some photoshop stuff
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$temp = self::jpegExtractMarker( $fh );
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if ( substr( $temp, 0, 14 ) === "Photoshop 3.0\x00" ) {
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$segments["PSIR"][] = $temp;
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}
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} elseif ( $buffer === "\xD9" || $buffer === "\xDA" ) {
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// EOI - end of image or SOS - start of scan. either way we're past any interesting segments
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return $segments;
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} else {
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// segment we don't care about, so skip
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$size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
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if ( $size['int'] < 2 ) {
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throw new MWException( "invalid marker size in jpeg" );
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}
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fseek( $fh, $size['int'] - 2, SEEK_CUR );
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}
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}
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// shouldn't get here.
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throw new MWException( "Reached end of jpeg file unexpectedly" );
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}
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/**
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* Helper function for jpegSegmentSplitter
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* @param resource &$fh File handle for JPEG file
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* @throws MWException
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* @return string Data content of segment.
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*/
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private static function jpegExtractMarker( &$fh ) {
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$size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
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if ( $size['int'] < 2 ) {
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throw new MWException( "invalid marker size in jpeg" );
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}
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if ( $size['int'] === 2 ) {
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// fread( ..., 0 ) generates a warning
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return '';
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}
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$segment = fread( $fh, $size['int'] - 2 );
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if ( strlen( $segment ) !== $size['int'] - 2 ) {
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throw new MWException( "Segment shorter than expected" );
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}
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return $segment;
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}
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/**
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* This reads the photoshop image resource.
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* Currently it only compares the iptc/iim hash
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* with the stored hash, which is used to determine the precedence
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* of the iptc data. In future it may extract some other info, like
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* url of copyright license.
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*
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* This should generally be called by BitmapMetadataHandler::doApp13()
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*
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* @param string $app13 Photoshop psir app13 block from jpg.
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* @throws MWException (It gets caught next level up though)
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* @return string If the iptc hash is good or not. One of 'iptc-no-hash',
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* 'iptc-good-hash', 'iptc-bad-hash'.
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*/
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public static function doPSIR( $app13 ) {
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if ( !$app13 ) {
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throw new MWException( "No App13 segment given" );
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}
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// First compare hash with real thing
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// 0x404 contains IPTC, 0x425 has hash
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// This is used to determine if the iptc is newer than
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// the xmp data, as xmp programs update the hash,
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// where non-xmp programs don't.
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$offset = 14; // skip past PHOTOSHOP 3.0 identifier. should already be checked.
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$appLen = strlen( $app13 );
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$realHash = "";
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$recordedHash = "";
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// the +12 is the length of an empty item.
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while ( $offset + 12 <= $appLen ) {
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$valid = true;
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if ( substr( $app13, $offset, 4 ) !== '8BIM' ) {
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// its supposed to be 8BIM
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// but apparently sometimes isn't esp. in
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// really old jpg's
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$valid = false;
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}
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$offset += 4;
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$id = substr( $app13, $offset, 2 );
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// id is a 2 byte id number which identifies
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// the piece of info this record contains.
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$offset += 2;
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// some record types can contain a name, which
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// is a pascal string 0-padded to be an even
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// number of bytes. Most times (and any time
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// we care) this is empty, making it two null bytes.
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$lenName = ord( substr( $app13, $offset, 1 ) ) + 1;
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// we never use the name so skip it. +1 for length byte
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if ( $lenName % 2 == 1 ) {
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$lenName++;
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} // pad to even.
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$offset += $lenName;
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// now length of data (unsigned long big endian)
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$lenData = wfUnpack( 'Nlen', substr( $app13, $offset, 4 ), 4 );
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// PHP can take issue with very large unsigned ints and make them negative.
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// Which should never ever happen, as this has to be inside a segment
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// which is limited to a 16 bit number.
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if ( $lenData['len'] < 0 ) {
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throw new MWException( "Too big PSIR (" . $lenData['len'] . ')' );
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}
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$offset += 4; // 4bytes length field;
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// this should not happen, but check.
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if ( $lenData['len'] + $offset > $appLen ) {
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throw new MWException( "PSIR data too long. (item length=" . $lenData['len']
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. "; offset=$offset; total length=$appLen)" );
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}
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if ( $valid ) {
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switch ( $id ) {
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case "\x04\x04":
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// IPTC block
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$realHash = md5( substr( $app13, $offset, $lenData['len'] ), true );
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break;
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case "\x04\x25":
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$recordedHash = substr( $app13, $offset, $lenData['len'] );
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break;
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}
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}
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// if odd, add 1 to length to account for
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// null pad byte.
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if ( $lenData['len'] % 2 == 1 ) {
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$lenData['len']++;
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}
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$offset += $lenData['len'];
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}
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if ( !$realHash || !$recordedHash ) {
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return 'iptc-no-hash';
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} elseif ( $realHash === $recordedHash ) {
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return 'iptc-good-hash';
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} else { /*$realHash !== $recordedHash */
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return 'iptc-bad-hash';
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}
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}
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}
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