includes/media/GIFMetadataExtractor.php

   1 <?php
   2 /**
   3  * GIF frame counter.
   4  *
   5  * Originally written in Perl by Steve Sanbeg.
   6  * Ported to PHP by Andrew Garrett
   7  * Deliberately not using MWExceptions to avoid external dependencies, encouraging
   8  * redistribution.
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License along
  21  * with this program; if not, write to the Free Software Foundation, Inc.,
  22  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  23  * http://www.gnu.org/copyleft/gpl.html
  24  *
  25  * @file
  26  * @ingroup Media
  27  */
  28
  29 /**
  30  * GIF frame counter.
  31  *
  32  * @ingroup Media
  33  */
  34 class GIFMetadataExtractor {
  35         static $gif_frame_sep;
  36         static $gif_extension_sep;
  37         static $gif_term;
  38
  39         const VERSION = 1;
  40
  41         // Each sub-block is less than or equal to 255 bytes.
  42         // Most of the time its 255 bytes, except for in XMP
  43         // blocks, where it's usually between 32-127 bytes each.
  44         const MAX_SUBBLOCKS = 262144; // 5mb divided by 20.
  45
  46         /**
  47          * @throws Exception
  48          * @param $filename string
  49          * @return array
  50          */
  51         static function getMetadata( $filename ) {
  52                 self::$gif_frame_sep = pack( "C", ord( "," ) );
  53                 self::$gif_extension_sep = pack( "C", ord( "!" ) );
  54                 self::$gif_term = pack( "C", ord( ";" ) );
  55
  56                 $frameCount = 0;
  57                 $duration = 0.0;
  58                 $isLooped = false;
  59                 $xmp = "";
  60                 $comment = array();
  61
  62                 if ( !$filename ) {
  63                         throw new Exception( "No file name specified" );
  64                 } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
  65                         throw new Exception( "File $filename does not exist" );
  66                 }
  67
  68                 $fh = fopen( $filename, 'rb' );
  69
  70                 if ( !$fh ) {
  71                         throw new Exception( "Unable to open file $filename" );
  72                 }
  73
  74                 // Check for the GIF header
  75                 $buf = fread( $fh, 6 );
  76                 if ( !( $buf == 'GIF87a' || $buf == 'GIF89a' ) ) {
  77                         throw new Exception( "Not a valid GIF file; header: $buf" );
  78                 }
  79
  80                 // Skip over width and height.
  81                 fread( $fh, 4 );
  82
  83                 // Read BPP
  84                 $buf = fread( $fh, 1 );
  85                 $bpp = self::decodeBPP( $buf );
  86
  87                 // Skip over background and aspect ratio
  88                 fread( $fh, 2 );
  89
  90                 // Skip over the GCT
  91                 self::readGCT( $fh, $bpp );
  92
  93                 while( !feof( $fh ) ) {
  94                         $buf = fread( $fh, 1 );
  95
  96                         if ( $buf == self::$gif_frame_sep ) {
  97                                 // Found a frame
  98                                 $frameCount++;
  99
 100                                 ## Skip bounding box
 101                                 fread( $fh, 8 );
 102
 103                                 ## Read BPP
 104                                 $buf = fread( $fh, 1 );
 105                                 $bpp = self::decodeBPP( $buf );
 106
 107                                 ## Read GCT
 108                                 self::readGCT( $fh, $bpp );
 109                                 fread( $fh, 1 );
 110                                 self::skipBlock( $fh );
 111                         } elseif ( $buf == self::$gif_extension_sep ) {
 112                                 $buf = fread( $fh, 1 );
 113                                 if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" );
 114                                 $extension_code = unpack( 'C', $buf );
 115                                 $extension_code = $extension_code[1];
 116
 117                                 if ( $extension_code == 0xF9 ) {
 118                                         // Graphics Control Extension.
 119                                         fread( $fh, 1 ); // Block size
 120
 121                                         fread( $fh, 1 ); // Transparency, disposal method, user input
 122
 123                                         $buf = fread( $fh, 2 ); // Delay, in hundredths of seconds.
 124                                         if ( strlen( $buf ) < 2 ) throw new Exception( "Ran out of input" );
 125                                         $delay = unpack( 'v', $buf );
 126                                         $delay = $delay[1];
 127                                         $duration += $delay * 0.01;
 128
 129                                         fread( $fh, 1 ); // Transparent colour index
 130
 131                                         $term = fread( $fh, 1 ); // Should be a terminator
 132                                         if ( strlen( $term ) < 1 ) throw new Exception( "Ran out of input" );
 133                                         $term = unpack( 'C', $term );
 134                                         $term = $term[1];
 135                                         if ( $term != 0 ) {
 136                                                 throw new Exception( "Malformed Graphics Control Extension block" );
 137                                         }
 138                                 } elseif ( $extension_code == 0xFE ) {
 139                                         // Comment block(s).
 140                                         $data = self::readBlock( $fh );
 141                                         if ( $data === "" ) {
 142                                                 throw new Exception( 'Read error, zero-length comment block' );
 143                                         }
 144
 145                                         // The standard says this should be ASCII, however its unclear if
 146                                         // thats true in practise. Check to see if its valid utf-8, if so
 147                                         // assume its that, otherwise assume its windows-1252 (iso-8859-1)
 148                                         $dataCopy = $data;
 149                                         // quickIsNFCVerify has the side effect of replacing any invalid characters
 150                                         UtfNormal::quickIsNFCVerify( $dataCopy );
 151
 152                                         if ( $dataCopy !== $data ) {
 153                                                 wfSuppressWarnings();
 154                                                 $data = iconv( 'windows-1252', 'UTF-8', $data );
 155                                                 wfRestoreWarnings();
 156                                         }
 157
 158                                         $commentCount = count( $comment );
 159                                         if ( $commentCount === 0
 160                                                 || $comment[$commentCount-1] !== $data )
 161                                         {
 162                                                 // Some applications repeat the same comment on each
 163                                                 // frame of an animated GIF image, so if this comment
 164                                                 // is identical to the last, only extract once.
 165                                                 $comment[] = $data;
 166                                         }
 167                                 } elseif ( $extension_code == 0xFF ) {
 168                                         // Application extension (Netscape info about the animated gif)
 169                                         // or XMP (or theoretically any other type of extension block)
 170                                         $blockLength = fread( $fh, 1 );
 171                                         if ( strlen( $blockLength ) < 1 ) throw new Exception( "Ran out of input" );
 172                                         $blockLength = unpack( 'C', $blockLength );
 173                                         $blockLength = $blockLength[1];
 174                                         $data = fread( $fh, $blockLength );
 175
 176                                         if ( $blockLength != 11 ) {
 177                                                 wfDebug( __METHOD__ . ' GIF application block with wrong length' );
 178                                                 fseek( $fh, -($blockLength + 1), SEEK_CUR );
 179                                                 self::skipBlock( $fh );
 180                                                 continue;
 181                                         }
 182
 183                                         // NETSCAPE2.0 (application name for animated gif)
 184                                         if ( $data == 'NETSCAPE2.0' ) {
 185                                                 $data = fread( $fh, 2 ); // Block length and introduction, should be 03 01
 186
 187                                                 if ( $data != "\x03\x01" ) {
 188                                                         throw new Exception( "Expected \x03\x01, got $data" );
 189                                                 }
 190
 191                                                 // Unsigned little-endian integer, loop count or zero for "forever"
 192                                                 $loopData = fread( $fh, 2 );
 193                                                 if ( strlen( $loopData ) < 2 ) throw new Exception( "Ran out of input" );
 194                                                 $loopData = unpack( 'v', $loopData );
 195                                                 $loopCount = $loopData[1];
 196
 197                                                 if ( $loopCount != 1 ) {
 198                                                         $isLooped = true;
 199                                                 }
 200
 201                                                 // Read out terminator byte
 202                                                 fread( $fh, 1 );
 203                                         } elseif ( $data == 'XMP DataXMP' ) {
 204                                                 // application name for XMP data.
 205                                                 // see pg 18 of XMP spec part 3.
 206
 207                                                 $xmp = self::readBlock( $fh, true );
 208
 209                                                 if ( substr( $xmp, -257, 3 ) !== "\x01\xFF\xFE"
 210                                                         || substr( $xmp, -4 ) !== "\x03\x02\x01\x00" )
 211                                                 {
 212                                                         // this is just a sanity check.
 213                                                         throw new Exception( "XMP does not have magic trailer!" );
 214                                                 }
 215
 216                                                 // strip out trailer.
 217                                                 $xmp = substr( $xmp, 0, -257 );
 218
 219                                         } else {
 220                                                 // unrecognized extension block
 221                                                 fseek( $fh, -($blockLength + 1), SEEK_CUR );
 222                                                 self::skipBlock( $fh );
 223                                                 continue;
 224                                         }
 225                                 } else {
 226                                         self::skipBlock( $fh );
 227                                 }
 228                         } elseif ( $buf == self::$gif_term ) {
 229                                 break;
 230                         } else {
 231                                 if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" );
 232                                 $byte = unpack( 'C', $buf );
 233                                 $byte = $byte[1];
 234                                 throw new Exception( "At position: " . ftell( $fh ) . ", Unknown byte " . $byte );
 235                         }
 236                 }
 237
 238                 return array(
 239                         'frameCount' => $frameCount,
 240                         'looped' => $isLooped,
 241                         'duration' => $duration,
 242                         'xmp' => $xmp,
 243                         'comment' => $comment,
 244                 );
 245         }
 246
 247         /**
 248          * @param $fh
 249          * @param $bpp
 250          * @return void
 251          */
 252         static function readGCT( $fh, $bpp ) {
 253                 if ( $bpp > 0 ) {
 254                         for( $i = 1; $i <= pow( 2, $bpp ); ++$i ) {
 255                                 fread( $fh, 3 );
 256                         }
 257                 }
 258         }
 259
 260         /**
 261          * @param $data
 262          * @throws Exception
 263          * @return int
 264          */
 265         static function decodeBPP( $data ) {
 266                 if ( strlen( $data ) < 1 ) throw new Exception( "Ran out of input" );
 267                 $buf = unpack( 'C', $data );
 268                 $buf = $buf[1];
 269                 $bpp = ( $buf & 7 ) + 1;
 270                 $buf >>= 7;
 271
 272                 $have_map = $buf & 1;
 273
 274                 return $have_map ? $bpp : 0;
 275         }
 276
 277         /**
 278          * @param $fh
 279          * @throws Exception
 280          */
 281         static function skipBlock( $fh ) {
 282                 while ( !feof( $fh ) ) {
 283                         $buf = fread( $fh, 1 );
 284                         if ( strlen( $buf ) < 1 ) throw new Exception( "Ran out of input" );
 285                         $block_len = unpack( 'C', $buf );
 286                         $block_len = $block_len[1];
 287                         if ( $block_len == 0 ) {
 288                                 return;
 289                         }
 290                         fread( $fh, $block_len );
 291                 }
 292         }
 293
 294         /**
 295          * Read a block. In the GIF format, a block is made up of
 296          * several sub-blocks. Each sub block starts with one byte
 297          * saying how long the sub-block is, followed by the sub-block.
 298          * The entire block is terminated by a sub-block of length
 299          * 0.
 300          * @param $fh FileHandle
 301          * @param $includeLengths Boolean Include the length bytes of the
 302          *  sub-blocks in the returned value. Normally this is false,
 303          *  except XMP is weird and does a hack where you need to keep
 304          *  these length bytes.
 305          * @throws Exception
 306          * @return string The data.
 307          */
 308         static function readBlock( $fh, $includeLengths = false ) {
 309                 $data = '';
 310                 $subLength = fread( $fh, 1 );
 311                 $blocks = 0;
 312
 313                 while( $subLength !== "\0" ) {
 314                         $blocks++;
 315                         if ( $blocks > self::MAX_SUBBLOCKS ) {
 316                                 throw new Exception( "MAX_SUBBLOCKS exceeded (over $blocks sub-blocks)" );
 317                         }
 318                         if ( feof( $fh ) ) {
 319                                 throw new Exception( "Read error: Unexpected EOF." );
 320                         }
 321                         if ( $includeLengths ) {
 322                                 $data .= $subLength;
 323                         }
 324
 325                         $data .= fread( $fh, ord( $subLength ) );
 326                         $subLength = fread( $fh, 1 );
 327                 }
 328                 return $data;
 329         }
 330
 331 }