/phase3/includes/media/JpegMetadataExtractor.php
PHP | 241 lines | 137 code | 25 blank | 79 comment | 34 complexity | 6a13dfd44946d02a67915b7d27b10135 MD5 | raw file
- <?php
- /**
- * Class for reading jpegs and extracting metadata.
- * see also BitmapMetadataHandler.
- *
- * Based somewhat on GIFMetadataExtrator.
- */
- class JpegMetadataExtractor {
- const MAX_JPEG_SEGMENTS = 200;
- // the max segment is a sanity check.
- // A jpeg file should never even remotely have
- // that many segments. Your average file has about 10.
- /** 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 of interesting segments.
- * @throws MWException if given invalid file.
- */
- static function segmentSplitter ( $filename ) {
- $showXMP = function_exists( 'xml_parser_create_ns' );
- $segmentCount = 0;
- $segments = array(
- 'XMP_ext' => array(),
- 'COM' => array(),
- );
- if ( !$filename ) {
- throw new MWException( "No filename specified for " . __METHOD__ );
- }
- if ( !file_exists( $filename ) || is_dir( $filename ) ) {
- throw new MWException( "Invalid file $filename passed to " . __METHOD__ );
- }
- $fh = fopen( $filename, "rb" );
- if ( !$fh ) {
- throw new MWException( "Could not open file $filename" );
- }
- $buffer = fread( $fh, 2 );
- if ( $buffer !== "\xFF\xD8" ) {
- throw new MWException( "Not a jpeg, no SOI" );
- }
- while ( !feof( $fh ) ) {
- $buffer = fread( $fh, 1 );
- $segmentCount++;
- if ( $segmentCount > self::MAX_JPEG_SEGMENTS ) {
- // this is just a sanity check
- throw new MWException( 'Too many jpeg segments. Aborting' );
- }
- if ( $buffer !== "\xFF" ) {
- throw new MWException( "Error reading jpeg file marker" );
- }
- $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::quickIsNFCVerify( $com );
- // turns $com to valid utf-8.
- // thus if no change, its utf-8, otherwise its something else.
- if ( $com !== $oldCom ) {
- wfSuppressWarnings();
- $com = $oldCom = iconv( 'windows-1252', 'UTF-8//IGNORE', $oldCom );
- wfRestoreWarnings();
- }
- // Try it again, if its still not a valid string, then probably
- // binary junk or some really weird encoding, so don't extract.
- UtfNormal::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 ) {
- $segments["XMP"] = substr( $temp, 29 );
- } elseif ( substr( $temp, 0, 35 ) === "http://ns.adobe.com/xmp/extension/\x00" && $showXMP ) {
- $segments["XMP_ext"][] = 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...
- $segments["XMP"] = substr( $temp, 29 );
- wfDebug( __METHOD__ . ' Found XMP section with wrong app identifier '
- . "Using anyways.\n" );
- } 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;
- } else {
- // segment we don't care about, so skip
- $size = unpack( "nint", fread( $fh, 2 ) );
- if ( $size['int'] <= 2 ) throw new MWException( "invalid marker size in jpeg" );
- fseek( $fh, $size['int'] - 2, SEEK_CUR );
- }
- }
- // shouldn't get here.
- throw new MWException( "Reached end of jpeg file unexpectedly" );
- }
- /**
- * Helper function for jpegSegmentSplitter
- * @param &$fh FileHandle for jpeg file
- * @return data content of segment.
- */
- private static function jpegExtractMarker( &$fh ) {
- $size = unpack( "nint", fread( $fh, 2 ) );
- if ( $size['int'] <= 2 ) throw new MWException( "invalid marker size in jpeg" );
- return fread( $fh, $size['int'] - 2 );
- }
- /**
- * 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.
- * @return String if the iptc hash is good or not.
- */
- public static function doPSIR ( $app13 ) {
- if ( !$app13 ) {
- return;
- }
- // 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' ) {
- // its 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)
- $lenData = unpack( 'Nlen', substr( $app13, $offset, 4 ) );
- $offset += 4; // 4bytes length field;
- // this should not happen, but check.
- if ( $lenData['len'] + $offset > $appLen ) {
- wfDebug( __METHOD__ . " PSIR data too long.\n" );
- return 'iptc-no-hash';
- }
- 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';
- } elseif ( $realHash === $recordedHash ) {
- return 'iptc-good-hash';
- } else { /*$realHash !== $recordedHash */
- return 'iptc-bad-hash';
- }
- }
- }