--- /dev/null
+<?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 );
+ }
+ }
+
+}
scripts.mit.edu / autoinstallsdev / mediawiki.git / blobdiff