diff options
Diffstat (limited to 'includes/media/GIFMetadataExtractor.php')
| -rw-r--r-- | includes/media/GIFMetadataExtractor.php | 236 |
1 files changed, 183 insertions, 53 deletions
diff --git a/includes/media/GIFMetadataExtractor.php b/includes/media/GIFMetadataExtractor.php index bc1a4804..5dbeb8f8 100644 --- a/includes/media/GIFMetadataExtractor.php +++ b/includes/media/GIFMetadataExtractor.php @@ -21,164 +21,294 @@ class GIFMetadataExtractor { static $gif_extension_sep; static $gif_term; + const VERSION = 1; + + // Each sub-block is less than or equal to 255 bytes. + // Most of the time its 255 bytes, except for in XMP + // blocks, where it's usually between 32-127 bytes each. + const MAX_SUBBLOCKS = 262144; // 5mb divided by 20. + + /** + * @throws Exception + * @param $filename string + * @return array + */ static function getMetadata( $filename ) { self::$gif_frame_sep = pack( "C", ord("," ) ); self::$gif_extension_sep = pack( "C", ord("!" ) ); self::$gif_term = pack( "C", ord(";" ) ); - + $frameCount = 0; $duration = 0.0; $isLooped = false; + $xmp = ""; + $comment = array(); - if (!$filename) + if ( !$filename ) { throw new Exception( "No file name specified" ); - elseif ( !file_exists($filename) || is_dir($filename) ) + } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) { throw new Exception( "File $filename does not exist" ); - - $fh = fopen( $filename, 'r' ); - - if (!$fh) + } + + $fh = fopen( $filename, 'rb' ); + + if ( !$fh ) { throw new Exception( "Unable to open file $filename" ); - + } + // Check for the GIF header $buf = fread( $fh, 6 ); if ( !($buf == 'GIF87a' || $buf == 'GIF89a') ) { throw new Exception( "Not a valid GIF file; header: $buf" ); } - + // Skip over width and height. fread( $fh, 4 ); - + // Read BPP $buf = fread( $fh, 1 ); $bpp = self::decodeBPP( $buf ); - + // Skip over background and aspect ratio fread( $fh, 2 ); - + // Skip over the GCT self::readGCT( $fh, $bpp ); - + while( !feof( $fh ) ) { $buf = fread( $fh, 1 ); - + if ($buf == self::$gif_frame_sep) { // Found a frame $frameCount++; - + ## Skip bounding box fread( $fh, 8 ); - + ## Read BPP $buf = fread( $fh, 1 ); $bpp = self::decodeBPP( $buf ); - + ## Read GCT self::readGCT( $fh, $bpp ); fread( $fh, 1 ); self::skipBlock( $fh ); } elseif ( $buf == self::$gif_extension_sep ) { $buf = fread( $fh, 1 ); + if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" ); $extension_code = unpack( 'C', $buf ); $extension_code = $extension_code[1]; - + if ($extension_code == 0xF9) { // Graphics Control Extension. fread( $fh, 1 ); // Block size - + fread( $fh, 1 ); // Transparency, disposal method, user input - + $buf = fread( $fh, 2 ); // Delay, in hundredths of seconds. + if ( strlen( $buf ) < 2 ) throw new Exception( "Ran out of input" ); $delay = unpack( 'v', $buf ); $delay = $delay[1]; $duration += $delay * 0.01; - + fread( $fh, 1 ); // Transparent colour index - + $term = fread( $fh, 1 ); // Should be a terminator + if ( strlen( $term ) < 1 ) throw new Exception( "Ran out of input" ); $term = unpack( 'C', $term ); $term = $term[1]; - if ($term != 0 ) + if ($term != 0 ) { throw new Exception( "Malformed Graphics Control Extension block" ); + } + } elseif ($extension_code == 0xFE) { + // Comment block(s). + $data = self::readBlock( $fh ); + if ( $data === "" ) { + throw new Exception( 'Read error, zero-length comment block' ); + } + + // The standard says this should be ASCII, however its unclear if + // thats true in practise. Check to see if its valid utf-8, if so + // assume its that, otherwise assume its windows-1252 (iso-8859-1) + $dataCopy = $data; + // quickIsNFCVerify has the side effect of replacing any invalid characters + UtfNormal::quickIsNFCVerify( $dataCopy ); + + if ( $dataCopy !== $data ) { + wfSuppressWarnings(); + $data = iconv( 'windows-1252', 'UTF-8', $data ); + wfRestoreWarnings(); + } + + $commentCount = count( $comment ); + if ( $commentCount === 0 + || $comment[$commentCount-1] !== $data ) + { + // Some applications repeat the same comment on each + // frame of an animated GIF image, so if this comment + // is identical to the last, only extract once. + $comment[] = $data; + } } elseif ($extension_code == 0xFF) { // Application extension (Netscape info about the animated gif) + // or XMP (or theoretically any other type of extension block) $blockLength = fread( $fh, 1 ); + if ( strlen( $blockLength ) < 1 ) throw new Exception( "Ran out of input" ); $blockLength = unpack( 'C', $blockLength ); $blockLength = $blockLength[1]; $data = fread( $fh, $blockLength ); - - // NETSCAPE2.0 (application name) - if ($blockLength != 11 || $data != 'NETSCAPE2.0') { + + if ($blockLength != 11 ) { + wfDebug( __METHOD__ . ' GIF application block with wrong length' ); fseek( $fh, -($blockLength + 1), SEEK_CUR ); self::skipBlock( $fh ); continue; } + + // NETSCAPE2.0 (application name for animated gif) + if ( $data == 'NETSCAPE2.0' ) { - $data = fread( $fh, 2 ); // Block length and introduction, should be 03 01 - - if ($data != "\x03\x01") { - throw new Exception( "Expected \x03\x01, got $data" ); - } - - // Unsigned little-endian integer, loop count or zero for "forever" - $loopData = fread( $fh, 2 ); - $loopData = unpack( 'v', $loopData ); - $loopCount = $loopData[1]; - - if ($loopCount != 1) { - $isLooped = true; + $data = fread( $fh, 2 ); // Block length and introduction, should be 03 01 + + if ($data != "\x03\x01") { + throw new Exception( "Expected \x03\x01, got $data" ); + } + + // Unsigned little-endian integer, loop count or zero for "forever" + $loopData = fread( $fh, 2 ); + if ( strlen( $loopData ) < 2 ) throw new Exception( "Ran out of input" ); + $loopData = unpack( 'v', $loopData ); + $loopCount = $loopData[1]; + + if ($loopCount != 1) { + $isLooped = true; + } + + // Read out terminator byte + fread( $fh, 1 ); + } elseif ( $data == 'XMP DataXMP' ) { + // application name for XMP data. + // see pg 18 of XMP spec part 3. + + $xmp = self::readBlock( $fh, true ); + + if ( substr( $xmp, -257, 3 ) !== "\x01\xFF\xFE" + || substr( $xmp, -4 ) !== "\x03\x02\x01\x00" ) + { + // this is just a sanity check. + throw new Exception( "XMP does not have magic trailer!" ); + } + + // strip out trailer. + $xmp = substr( $xmp, 0, -257 ); + + } else { + // unrecognized extension block + fseek( $fh, -($blockLength + 1), SEEK_CUR ); + self::skipBlock( $fh ); + continue; } - - // Read out terminator byte - fread( $fh, 1 ); } else { self::skipBlock( $fh ); } } elseif ( $buf == self::$gif_term ) { break; } else { + if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" ); $byte = unpack( 'C', $buf ); $byte = $byte[1]; throw new Exception( "At position: ".ftell($fh). ", Unknown byte ".$byte ); } } - + return array( 'frameCount' => $frameCount, 'looped' => $isLooped, - 'duration' => $duration + 'duration' => $duration, + 'xmp' => $xmp, + 'comment' => $comment, ); - } - + + /** + * @param $fh + * @param $bpp + * @return void + */ static function readGCT( $fh, $bpp ) { - if ($bpp > 0) { - for( $i=1; $i<=pow(2,$bpp); ++$i ) { + if ( $bpp > 0 ) { + for( $i=1; $i<=pow( 2, $bpp ); ++$i ) { fread( $fh, 3 ); } } } - + + /** + * @param $data + * @return int + */ static function decodeBPP( $data ) { + if ( strlen( $data ) < 1 ) throw new Exception( "Ran out of input" ); $buf = unpack( 'C', $data ); $buf = $buf[1]; $bpp = ( $buf & 7 ) + 1; $buf >>= 7; - + $have_map = $buf & 1; - + return $have_map ? $bpp : 0; } - + + /** + * @param $fh + * @return + */ static function skipBlock( $fh ) { while ( !feof( $fh ) ) { $buf = fread( $fh, 1 ); + if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" ); $block_len = unpack( 'C', $buf ); $block_len = $block_len[1]; - if ($block_len == 0) + if ($block_len == 0) { return; + } fread( $fh, $block_len ); } } + /** + * Read a block. In the GIF format, a block is made up of + * several sub-blocks. Each sub block starts with one byte + * saying how long the sub-block is, followed by the sub-block. + * The entire block is terminated by a sub-block of length + * 0. + * @param $fh FileHandle + * @param $includeLengths Boolean Include the length bytes of the + * sub-blocks in the returned value. Normally this is false, + * except XMP is weird and does a hack where you need to keep + * these length bytes. + * @return The data. + */ + static function readBlock( $fh, $includeLengths = false ) { + $data = ''; + $subLength = fread( $fh, 1 ); + $blocks = 0; + + while( $subLength !== "\0" ) { + $blocks++; + if ( $blocks > self::MAX_SUBBLOCKS ) { + throw new Exception( "MAX_SUBBLOCKS exceeded (over $blocks sub-blocks)" ); + } + if ( feof( $fh ) ) { + throw new Exception( "Read error: Unexpected EOF." ); + } + if ( $includeLengths ) { + $data .= $subLength; + } + + $data .= fread( $fh, ord( $subLength ) ); + $subLength = fread( $fh, 1 ); + } + return $data; + } } |