(bug 16451) Fix application of scaling limits for animated GIFs.
authorAndrew Garrett <werdna@users.mediawiki.org>
Mon, 3 Aug 2009 15:01:51 +0000 (15:01 +0000)
committerAndrew Garrett <werdna@users.mediawiki.org>
Mon, 3 Aug 2009 15:01:51 +0000 (15:01 +0000)
* Creates a new media handler for GIF files, and extracts metadata such as duration, whether or not the GIF is looped, and the number of frames.
* Uses the extracted metadata for the long file description.
* Considers number of frames in the calculation of image area (multiplies by width and height to get the "time-area", or so to speak).

After this patch is deployed, the work-around to disable GIF scaling on Wikimedia sites can be eliminated.

includes/AutoLoader.php
includes/DefaultSettings.php
includes/media/Bitmap.php
includes/media/GIF.php [new file with mode: 0644]
includes/media/GIFMetadataExtractor.php [new file with mode: 0644]
languages/messages/MessagesEn.php

index 39db06e..ef2bda1 100644 (file)
@@ -87,6 +87,8 @@ $wgAutoloadLocalClasses = array(
        'ForkController' => 'includes/ForkController.php',
        'FormatExif' => 'includes/Exif.php',
        'FormOptions' => 'includes/FormOptions.php',
+       'GIFMetadataExtractor' => 'includes/media/GIFMetadataExtractor.php',
+       'GIFHandler' => 'includes/media/GIF.php',
        'GlobalDependency' => 'includes/CacheDependency.php',
        'HashBagOStuff' => 'includes/BagOStuff.php',
        'HashtableReplacer' => 'includes/StringUtils.php',
index fe142ae..d16d97a 100644 (file)
@@ -2129,7 +2129,7 @@ $wgSiteNotice = '';
 $wgMediaHandlers = array(
        'image/jpeg' => 'BitmapHandler',
        'image/png' => 'BitmapHandler',
-       'image/gif' => 'BitmapHandler',
+       'image/gif' => 'GIFHandler',
        'image/tiff' => 'TiffHandler',
        'image/x-ms-bmp' => 'BmpHandler',
        'image/x-bmp' => 'BmpHandler',
index 7144ebd..d4a7c35 100644 (file)
@@ -22,7 +22,7 @@ class BitmapHandler extends ImageHandler {
                # JPEG has the handy property of allowing thumbnailing without full decompression, so we make
                # an exception for it.
                if ( $mimeType !== 'image/jpeg' &&
-                       $srcWidth * $srcHeight > $wgMaxImageArea )
+                       $this->getImageArea( $image, $srcWidth, $srcHeight ) > $wgMaxImageArea )
                {
                        return false;
                }
@@ -39,6 +39,13 @@ class BitmapHandler extends ImageHandler {
 
                return true;
        }
+       
+       
+       // Function that returns the number of pixels to be thumbnailed.
+       // Intended for animated GIFs to multiply by the number of frames.
+       function getImageArea( $image, $width, $height ) {
+               return $width * $height;
+       }
 
        function doTransform( $image, $dstPath, $dstUrl, $params, $flags = 0 ) {
                global $wgUseImageMagick, $wgImageMagickConvertCommand, $wgImageMagickTempDir;
diff --git a/includes/media/GIF.php b/includes/media/GIF.php
new file mode 100644 (file)
index 0000000..b5c62ee
--- /dev/null
@@ -0,0 +1,58 @@
+<?php
+/**
+ * @file
+ * @ingroup Media
+ */
+
+/**
+ * Handler for GIF images.
+ *
+ * @ingroup Media
+ */
+class GIFHandler extends BitmapHandler {
+       
+       function getMetadata( $image, $filename ) {
+               if ( !isset($image->parsedGIFMetadata) )
+                       $image->parsedGIFMetadata = GIFMetadataExtractor::getMetadata( $filename );
+
+               return serialize($image->parsedGIFMetadata);                    
+
+       }
+       
+       function formatMetadata( $image ) {
+               return false;
+       }
+       
+       function getImageArea( $image, $width, $height ) {
+               $metadata = unserialize($image->getMetadata());
+               return $width * $height * $metadata['frameCount'];
+       }
+       
+       function getMetadataType( $image ) {
+               return 'parsed-gif';
+       }
+       
+       function getLongDesc( $image ) {
+               global $wgUser, $wgLang;
+               $sk = $wgUser->getSkin();
+               
+               $metadata = unserialize($image->getMetadata());
+               
+               $info = array();
+               $info[] = $image->getMimeType();
+               $info[] = $sk->formatSize( $image->getSize() );
+               
+               if ($metadata['looped'])
+                       $info[] = wfMsgExt( 'file-info-gif-looped', 'parseinline' );
+               
+               if ($metadata['frameCount'] > 1)
+                       $info[] = wfMsgExt( 'file-info-gif-frames', 'parseinline', $metadata['frameCount'] );
+               
+               if ($metadata['duration'])
+                       $info[] = $wgLang->formatTimePeriod( $metadata['duration'] );
+               
+               $infoString = $wgLang->commaList( $info );
+               
+               return "($infoString)";
+       }
+}
diff --git a/includes/media/GIFMetadataExtractor.php b/includes/media/GIFMetadataExtractor.php
new file mode 100644 (file)
index 0000000..3f17871
--- /dev/null
@@ -0,0 +1,171 @@
+<?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( $filename ) {
+               wfProfileIn( __METHOD__ );
+       
+               self::$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 dimensions (Why is this 8 bytes and not 4?)
+                               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') {
+                                               self::skipBlock();
+                                               continue;
+                                       }
+                                       
+                                       fread( $fh, 2 ); // Block length and introduction, should be 03 01
+                                       
+                                       // 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 );
+                               }
+                       } elseif ( $buf == self::$gif_term ) {
+                               break;
+                       } else {
+                               $byte = unpack( 'C', $buf );
+                               $byte = $byte[1];
+                               throw new Exception( "At position: ".ftell($fh). ", Unknown byte ".$byte );
+                       }
+               }
+               
+               wfProfileOut( __METHOD__ );
+               
+               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 );
+               }
+       }
+
+}
\ No newline at end of file
index cd97fb8..4988c93 100644 (file)
@@ -3411,6 +3411,8 @@ $1',
 'svg-long-desc'        => '(SVG file, nominally $1 × $2 pixels, file size: $3)',
 'show-big-image'       => 'Full resolution',
 'show-big-image-thumb' => '<small>Size of this preview: $1 × $2 pixels</small>',
+'file-info-gif-looped' => 'looped',
+'file-info-gif-frames' => '$1 frames',
 
 # Special:NewFiles
 'newimages'             => 'Gallery of new files',