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JpegMetadataExtractor.php
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JpegMetadataExtractor.php
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<?php
/**
* Extraction of JPEG image metadata.
*
* 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; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Media
*/
use MediaWiki\Libs\UnpackFailedException;
use Wikimedia\AtEase\AtEase;
use Wikimedia\XMPReader\Reader as XMPReader;
/**
* Class for reading jpegs and extracting metadata.
* see also BitmapMetadataHandler.
*
* Based somewhat on GIFMetadataExtractor.
*
* @ingroup Media
*/
class JpegMetadataExtractor {
/**
* The max segment is a safety check. A JPEG file should never even remotely have
* that many segments. Your average file has about 10.
*/
private const MAX_JPEG_SEGMENTS = 200;
/** Function to extract metadata segments of interest from jpeg files
* based on GIFMetadataExtractor.
*
* we can almost use getimagesize to do this
* but gis doesn't support having multiple app1 segments
* and those can't extract xmp on files containing both exif and xmp data
*
* @param string $filename Name of jpeg file
* @return array Array of interesting segments.
* @throws InvalidJpegException
*/
public static function segmentSplitter( $filename ) {
$showXMP = XMPReader::isSupported();
$segmentCount = 0;
$segments = [
'XMP_ext' => [],
'COM' => [],
'PSIR' => [],
];
if ( !$filename ) {
throw new InvalidJpegException( "No filename specified for " . __METHOD__ );
}
if ( !file_exists( $filename ) || is_dir( $filename ) ) {
throw new InvalidJpegException( "Invalid file $filename passed to " . __METHOD__ );
}
$fh = fopen( $filename, "rb" );
if ( !$fh ) {
throw new InvalidJpegException( "Could not open file $filename" );
}
$buffer = fread( $fh, 2 );
if ( $buffer !== "\xFF\xD8" ) {
throw new InvalidJpegException( "Not a jpeg, no SOI" );
}
while ( !feof( $fh ) ) {
$buffer = fread( $fh, 1 );
$segmentCount++;
if ( $segmentCount > self::MAX_JPEG_SEGMENTS ) {
throw new InvalidJpegException( 'Too many jpeg segments. Aborting' );
}
while ( $buffer !== "\xFF" && !feof( $fh ) ) {
// 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.
$buffer = fread( $fh, 1 );
}
$buffer = fread( $fh, 1 );
while ( $buffer === "\xFF" && !feof( $fh ) ) {
// Skip through any 0xFF padding bytes.
$buffer = fread( $fh, 1 );
}
if ( $buffer === "\xFE" ) {
// COM section -- file comment
// First see if valid utf-8,
// if not try to convert it to windows-1252.
$com = $oldCom = trim( self::jpegExtractMarker( $fh ) );
UtfNormal\Validator::quickIsNFCVerify( $com );
// turns $com to valid utf-8.
// thus if no change, it's utf-8, otherwise it's something else.
if ( $com !== $oldCom ) {
AtEase::suppressWarnings();
$com = $oldCom = iconv( 'windows-1252', 'UTF-8//IGNORE', $oldCom );
AtEase::restoreWarnings();
}
// Try it again, if it's still not a valid string, then probably
// binary junk or some really weird encoding, so don't extract.
UtfNormal\Validator::quickIsNFCVerify( $com );
if ( $com === $oldCom ) {
$segments["COM"][] = $oldCom;
} else {
wfDebug( __METHOD__ . " Ignoring JPEG comment as is garbage." );
}
} elseif ( $buffer === "\xE1" ) {
// APP1 section (Exif, XMP, and XMP extended)
// only extract if XMP is enabled.
$temp = self::jpegExtractMarker( $fh );
// check what type of app segment this is.
if ( substr( $temp, 0, 29 ) === "http://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
// use trim to remove trailing \0 chars
$segments["XMP"] = trim( substr( $temp, 29 ) );
} elseif ( substr( $temp, 0, 35 ) === "http://ns.adobe.com/xmp/extension/\x00" && $showXMP ) {
// use trim to remove trailing \0 chars
$segments["XMP_ext"][] = trim( substr( $temp, 35 ) );
} elseif ( substr( $temp, 0, 29 ) === "XMP\x00://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
// Some images (especially flickr images) seem to have this.
// I really have no idea what the deal is with them, but
// whatever...
// use trim to remove trailing \0 chars
$segments["XMP"] = trim( substr( $temp, 29 ) );
wfDebug( __METHOD__ . ' Found XMP section with wrong app identifier '
. "Using anyways." );
} elseif ( substr( $temp, 0, 6 ) === "Exif\0\0" ) {
// Just need to find out what the byte order is.
// because php's exif plugin sucks...
// This is a II for little Endian, MM for big. Not a unicode BOM.
$byteOrderMarker = substr( $temp, 6, 2 );
if ( $byteOrderMarker === 'MM' ) {
$segments['byteOrder'] = 'BE';
} elseif ( $byteOrderMarker === 'II' ) {
$segments['byteOrder'] = 'LE';
} else {
wfDebug( __METHOD__ . " Invalid byte ordering?!" );
}
}
} elseif ( $buffer === "\xED" ) {
// APP13 - PSIR. IPTC and some photoshop stuff
$temp = self::jpegExtractMarker( $fh );
if ( substr( $temp, 0, 14 ) === "Photoshop 3.0\x00" ) {
$segments["PSIR"][] = $temp;
}
} elseif ( $buffer === "\xD9" || $buffer === "\xDA" ) {
// EOI - end of image or SOS - start of scan. either way we're past any interesting segments
return $segments;
} elseif ( in_array( $buffer, [
"\xC0", "\xC1", "\xC2", "\xC3", "\xC5", "\xC6", "\xC7",
"\xC9", "\xCA", "\xCB", "\xCD", "\xCE", "\xCF" ] )
) {
// SOF0, SOF1, SOF2, ... (same list as getimagesize)
$temp = self::jpegExtractMarker( $fh );
try {
$segments["SOF"] = StringUtils::unpack( 'Cbits/nheight/nwidth/Ccomponents', $temp );
} catch ( UnpackFailedException $e ) {
throw new InvalidJpegException( $e->getMessage() );
}
} else {
// segment we don't care about, so skip
try {
$size = StringUtils::unpack( "nint", fread( $fh, 2 ), 2 );
} catch ( UnpackFailedException $e ) {
throw new InvalidJpegException( $e->getMessage() );
}
if ( $size['int'] < 2 ) {
throw new InvalidJpegException( "invalid marker size in jpeg" );
}
// Note it's possible to seek beyond end of file if truncated.
// fseek doesn't report a failure in this case.
fseek( $fh, $size['int'] - 2, SEEK_CUR );
}
}
// shouldn't get here.
throw new InvalidJpegException( "Reached end of jpeg file unexpectedly" );
}
/**
* Helper function for jpegSegmentSplitter
* @param resource &$fh File handle for JPEG file
* @throws InvalidJpegException
* @return string Data content of segment.
*/
private static function jpegExtractMarker( &$fh ) {
try {
$size = StringUtils::unpack( "nint", fread( $fh, 2 ), 2 );
} catch ( UnpackFailedException $e ) {
throw new InvalidJpegException( $e->getMessage() );
}
if ( $size['int'] < 2 ) {
throw new InvalidJpegException( "invalid marker size in jpeg" );
}
if ( $size['int'] === 2 ) {
// fread( ..., 0 ) generates a warning
return '';
}
$segment = fread( $fh, $size['int'] - 2 );
if ( strlen( $segment ) !== $size['int'] - 2 ) {
throw new InvalidJpegException( "Segment shorter than expected" );
}
return $segment;
}
/**
* This reads the photoshop image resource.
* Currently it only compares the iptc/iim hash
* with the stored hash, which is used to determine the precedence
* of the iptc data. In future it may extract some other info, like
* url of copyright license.
*
* This should generally be called by BitmapMetadataHandler::doApp13()
*
* @param string $app13 Photoshop psir app13 block from jpg.
* @throws InvalidPSIRException
* @return string If the iptc hash is good or not. One of 'iptc-no-hash',
* 'iptc-good-hash', 'iptc-bad-hash'.
*/
public static function doPSIR( $app13 ) {
if ( !$app13 ) {
throw new InvalidPSIRException( "No App13 segment given" );
}
// First compare hash with real thing
// 0x404 contains IPTC, 0x425 has hash
// This is used to determine if the iptc is newer than
// the xmp data, as xmp programs update the hash,
// where non-xmp programs don't.
$offset = 14; // skip past PHOTOSHOP 3.0 identifier. should already be checked.
$appLen = strlen( $app13 );
$realHash = "";
$recordedHash = "";
// the +12 is the length of an empty item.
while ( $offset + 12 <= $appLen ) {
$valid = true;
if ( substr( $app13, $offset, 4 ) !== '8BIM' ) {
// it's supposed to be 8BIM
// but apparently sometimes isn't esp. in
// really old jpg's
$valid = false;
}
$offset += 4;
$id = substr( $app13, $offset, 2 );
// id is a 2 byte id number which identifies
// the piece of info this record contains.
$offset += 2;
// some record types can contain a name, which
// is a pascal string 0-padded to be an even
// number of bytes. Most times (and any time
// we care) this is empty, making it two null bytes.
$lenName = ord( substr( $app13, $offset, 1 ) ) + 1;
// we never use the name so skip it. +1 for length byte
if ( $lenName % 2 === 1 ) {
$lenName++;
} // pad to even.
$offset += $lenName;
// now length of data (unsigned long big endian)
try {
$lenData = StringUtils::unpack( 'Nlen', substr( $app13, $offset, 4 ), 4 );
} catch ( UnpackFailedException $e ) {
throw new InvalidPSIRException( $e->getMessage() );
}
// PHP can take issue with very large unsigned ints and make them negative.
// Which should never ever happen, as this has to be inside a segment
// which is limited to a 16 bit number.
if ( $lenData['len'] < 0 ) {
throw new InvalidPSIRException( "Too big PSIR (" . $lenData['len'] . ')' );
}
$offset += 4; // 4bytes length field;
// this should not happen, but check.
if ( $lenData['len'] + $offset > $appLen ) {
throw new InvalidPSIRException( "PSIR data too long. (item length=" . $lenData['len']
. "; offset=$offset; total length=$appLen)" );
}
if ( $valid ) {
switch ( $id ) {
case "\x04\x04":
// IPTC block
$realHash = md5( substr( $app13, $offset, $lenData['len'] ), true );
break;
case "\x04\x25":
$recordedHash = substr( $app13, $offset, $lenData['len'] );
break;
}
}
// if odd, add 1 to length to account for
// null pad byte.
if ( $lenData['len'] % 2 === 1 ) {
$lenData['len']++;
}
$offset += $lenData['len'];
}
if ( !$realHash || !$recordedHash ) {
return 'iptc-no-hash';
}
if ( $realHash === $recordedHash ) {
return 'iptc-good-hash';
}
/* if $realHash !== $recordedHash */
return 'iptc-bad-hash';
}
}

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JpegMetadataExtractor.php (10 KB)

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