diff options
Diffstat (limited to 'includes/media/GIFMetadataExtractor.php')
-rw-r--r-- | includes/media/GIFMetadataExtractor.php | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/includes/media/GIFMetadataExtractor.php b/includes/media/GIFMetadataExtractor.php new file mode 100644 index 00000000..fac9012b --- /dev/null +++ b/includes/media/GIFMetadataExtractor.php @@ -0,0 +1,175 @@ +<?php +/** + * GIF frame counter. + * Originally written in Perl by Steve Sanbeg. + * Ported to PHP by Andrew Garrett + * Deliberately not using MWExceptions to avoid external dependencies, encouraging + * redistribution. + */ + +class GIFMetadataExtractor { + static $gif_frame_sep; + static $gif_extension_sep; + static $gif_term; + + 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; + $isLooped = false; + + if (!$filename) + throw new Exception( "No file name specified" ); + elseif ( !file_exists($filename) || is_dir($filename) ) + throw new Exception( "File $filename does not exist" ); + + $fh = fopen( $filename, 'r' ); + + if (!$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 ); + $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. + $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 + $term = unpack( 'C', $term ); + $term = $term[1]; + if ($term != 0 ) + throw new Exception( "Malformed Graphics Control Extension block" ); + } elseif ($extension_code == 0xFF) { + // Application extension (Netscape info about the animated gif) + $blockLength = fread( $fh, 1 ); + $blockLength = unpack( 'C', $blockLength ); + $blockLength = $blockLength[1]; + $data = fread( $fh, $blockLength ); + + // NETSCAPE2.0 (application name) + if ($blockLength != 11 || $data != 'NETSCAPE2.0') { + fseek( $fh, -($blockLength + 1), SEEK_CUR ); + self::skipBlock( $fh ); + continue; + } + + $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; + } + + // Read out terminator byte + fread( $fh, 1 ); + } else { + self::skipBlock( $fh ); + } + } elseif ( $buf == self::$gif_term ) { + break; + } else { + $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 + ); + + } + + static function readGCT( $fh, $bpp ) { + if ($bpp > 0) { + for( $i=1; $i<=pow(2,$bpp); ++$i ) { + fread( $fh, 3 ); + } + } + } + + static function decodeBPP( $data ) { + $buf = unpack( 'C', $data ); + $buf = $buf[1]; + $bpp = ( $buf & 7 ) + 1; + $buf >>= 7; + + $have_map = $buf & 1; + + return $have_map ? $bpp : 0; + } + + static function skipBlock( $fh ) { + while ( !feof( $fh ) ) { + $buf = fread( $fh, 1 ); + $block_len = unpack( 'C', $buf ); + $block_len = $block_len[1]; + if ($block_len == 0) + return; + fread( $fh, $block_len ); + } + } + +} |