includes/media/PNGMetadataExtractor.php

   1 <?php
   2 /**
   3  * PNG frame counter and metadata extractor.
   4  *
   5  * Slightly derived from GIFMetadataExtractor.php
   6  * Deliberately not using MWExceptions to avoid external dependencies, encouraging
   7  * redistribution.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Media
  26  */
  27
  28 /**
  29  * PNG frame counter.
  30  *
  31  * @ingroup Media
  32  */
  33 class PNGMetadataExtractor {
  34         /** @var string */
  35         private static $pngSig;
  36
  37         /** @var int */
  38         private static $crcSize;
  39
  40         /** @var array */
  41         private static $textChunks;
  42
  43         const VERSION = 1;
  44         const MAX_CHUNK_SIZE = 3145728; // 3 megabytes
  45
  46         static function getMetadata( $filename ) {
  47                 self::$pngSig = pack( "C8", 137, 80, 78, 71, 13, 10, 26, 10 );
  48                 self::$crcSize = 4;
  49                 /* based on list at http://owl.phy.queensu.ca/~phil/exiftool/TagNames/PNG.html#TextualData
  50                  * and https://www.w3.org/TR/PNG/#11keywords
  51                  */
  52                 self::$textChunks = [
  53                         'xml:com.adobe.xmp' => 'xmp',
  54                         # Artist is unofficial. Author is the recommended
  55                         # keyword in the PNG spec. However some people output
  56                         # Artist so support both.
  57                         'artist' => 'Artist',
  58                         'model' => 'Model',
  59                         'make' => 'Make',
  60                         'author' => 'Artist',
  61                         'comment' => 'PNGFileComment',
  62                         'description' => 'ImageDescription',
  63                         'title' => 'ObjectName',
  64                         'copyright' => 'Copyright',
  65                         # Source as in original device used to make image
  66                         # not as in who gave you the image
  67                         'source' => 'Model',
  68                         'software' => 'Software',
  69                         'disclaimer' => 'Disclaimer',
  70                         'warning' => 'ContentWarning',
  71                         'url' => 'Identifier', # Not sure if this is best mapping. Maybe WebStatement.
  72                         'label' => 'Label',
  73                         'creation time' => 'DateTimeDigitized',
  74                         /* Other potentially useful things - Document */
  75                 ];
  76
  77                 $frameCount = 0;
  78                 $loopCount = 1;
  79                 $text = [];
  80                 $duration = 0.0;
  81                 $bitDepth = 0;
  82                 $colorType = 'unknown';
  83
  84                 if ( !$filename ) {
  85                         throw new Exception( __METHOD__ . ": No file name specified" );
  86                 } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
  87                         throw new Exception( __METHOD__ . ": File $filename does not exist" );
  88                 }
  89
  90                 $fh = fopen( $filename, 'rb' );
  91
  92                 if ( !$fh ) {
  93                         throw new Exception( __METHOD__ . ": Unable to open file $filename" );
  94                 }
  95
  96                 // Check for the PNG header
  97                 $buf = fread( $fh, 8 );
  98                 if ( $buf != self::$pngSig ) {
  99                         throw new Exception( __METHOD__ . ": Not a valid PNG file; header: $buf" );
 100                 }
 101
 102                 // Read chunks
 103                 while ( !feof( $fh ) ) {
 104                         $buf = fread( $fh, 4 );
 105                         if ( !$buf || strlen( $buf ) < 4 ) {
 106                                 throw new Exception( __METHOD__ . ": Read error" );
 107                         }
 108                         $chunk_size = unpack( "N", $buf )[1];
 109
 110                         if ( $chunk_size < 0 ) {
 111                                 throw new Exception( __METHOD__ . ": Chunk size too big for unpack" );
 112                         }
 113
 114                         $chunk_type = fread( $fh, 4 );
 115                         if ( !$chunk_type || strlen( $chunk_type ) < 4 ) {
 116                                 throw new Exception( __METHOD__ . ": Read error" );
 117                         }
 118
 119                         if ( $chunk_type == "IHDR" ) {
 120                                 $buf = self::read( $fh, $chunk_size );
 121                                 if ( !$buf || strlen( $buf ) < $chunk_size ) {
 122                                         throw new Exception( __METHOD__ . ": Read error" );
 123                                 }
 124                                 $width = unpack( 'N', substr( $buf, 0, 4 ) )[1];
 125                                 $height = unpack( 'N', substr( $buf, 4, 4 ) )[1];
 126                                 $bitDepth = ord( substr( $buf, 8, 1 ) );
 127                                 // Detect the color type in British English as per the spec
 128                                 // https://www.w3.org/TR/PNG/#11IHDR
 129                                 switch ( ord( substr( $buf, 9, 1 ) ) ) {
 130                                         case 0:
 131                                                 $colorType = 'greyscale';
 132                                                 break;
 133                                         case 2:
 134                                                 $colorType = 'truecolour';
 135                                                 break;
 136                                         case 3:
 137                                                 $colorType = 'index-coloured';
 138                                                 break;
 139                                         case 4:
 140                                                 $colorType = 'greyscale-alpha';
 141                                                 break;
 142                                         case 6:
 143                                                 $colorType = 'truecolour-alpha';
 144                                                 break;
 145                                         default:
 146                                                 $colorType = 'unknown';
 147                                                 break;
 148                                 }
 149                         } elseif ( $chunk_type == "acTL" ) {
 150                                 $buf = fread( $fh, $chunk_size );
 151                                 if ( !$buf || strlen( $buf ) < $chunk_size || $chunk_size < 4 ) {
 152                                         throw new Exception( __METHOD__ . ": Read error" );
 153                                 }
 154
 155                                 $actl = unpack( "Nframes/Nplays", $buf );
 156                                 $frameCount = $actl['frames'];
 157                                 $loopCount = $actl['plays'];
 158                         } elseif ( $chunk_type == "fcTL" ) {
 159                                 $buf = self::read( $fh, $chunk_size );
 160                                 if ( !$buf || strlen( $buf ) < $chunk_size ) {
 161                                         throw new Exception( __METHOD__ . ": Read error" );
 162                                 }
 163                                 $buf = substr( $buf, 20 );
 164                                 if ( strlen( $buf ) < 4 ) {
 165                                         throw new Exception( __METHOD__ . ": Read error" );
 166                                 }
 167
 168                                 $fctldur = unpack( "ndelay_num/ndelay_den", $buf );
 169                                 if ( $fctldur['delay_den'] == 0 ) {
 170                                         $fctldur['delay_den'] = 100;
 171                                 }
 172                                 if ( $fctldur['delay_num'] ) {
 173                                         $duration += $fctldur['delay_num'] / $fctldur['delay_den'];
 174                                 }
 175                         } elseif ( $chunk_type == "iTXt" ) {
 176                                 // Extracts iTXt chunks, uncompressing if necessary.
 177                                 $buf = self::read( $fh, $chunk_size );
 178                                 $items = [];
 179                                 if ( preg_match(
 180                                         '/^([^\x00]{1,79})\x00(\x00|\x01)\x00([^\x00]*)(.)[^\x00]*\x00(.*)$/Ds',
 181                                         $buf, $items )
 182                                 ) {
 183                                         /* $items[1] = text chunk name, $items[2] = compressed flag,
 184                                          * $items[3] = lang code (or ""), $items[4]= compression type.
 185                                          * $items[5] = content
 186                                          */
 187
 188                                         // Theoretically should be case-sensitive, but in practise...
 189                                         $items[1] = strtolower( $items[1] );
 190                                         if ( !isset( self::$textChunks[$items[1]] ) ) {
 191                                                 // Only extract textual chunks on our list.
 192                                                 fseek( $fh, self::$crcSize, SEEK_CUR );
 193                                                 continue;
 194                                         }
 195
 196                                         $items[3] = strtolower( $items[3] );
 197                                         if ( $items[3] == '' ) {
 198                                                 // if no lang specified use x-default like in xmp.
 199                                                 $items[3] = 'x-default';
 200                                         }
 201
 202                                         // if compressed
 203                                         if ( $items[2] == "\x01" ) {
 204                                                 if ( function_exists( 'gzuncompress' ) && $items[4] === "\x00" ) {
 205                                                         MediaWiki\suppressWarnings();
 206                                                         $items[5] = gzuncompress( $items[5] );
 207                                                         MediaWiki\restoreWarnings();
 208
 209                                                         if ( $items[5] === false ) {
 210                                                                 // decompression failed
 211                                                                 wfDebug( __METHOD__ . ' Error decompressing iTxt chunk - ' . $items[1] . "\n" );
 212                                                                 fseek( $fh, self::$crcSize, SEEK_CUR );
 213                                                                 continue;
 214                                                         }
 215                                                 } else {
 216                                                         wfDebug( __METHOD__ . ' Skipping compressed png iTXt chunk due to lack of zlib,'
 217                                                                 . " or potentially invalid compression method\n" );
 218                                                         fseek( $fh, self::$crcSize, SEEK_CUR );
 219                                                         continue;
 220                                                 }
 221                                         }
 222                                         $finalKeyword = self::$textChunks[$items[1]];
 223                                         $text[$finalKeyword][$items[3]] = $items[5];
 224                                         $text[$finalKeyword]['_type'] = 'lang';
 225                                 } else {
 226                                         // Error reading iTXt chunk
 227                                         throw new Exception( __METHOD__ . ": Read error on iTXt chunk" );
 228                                 }
 229                         } elseif ( $chunk_type == 'tEXt' ) {
 230                                 $buf = self::read( $fh, $chunk_size );
 231
 232                                 // In case there is no \x00 which will make explode fail.
 233                                 if ( strpos( $buf, "\x00" ) === false ) {
 234                                         throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
 235                                 }
 236
 237                                 list( $keyword, $content ) = explode( "\x00", $buf, 2 );
 238                                 if ( $keyword === '' || $content === '' ) {
 239                                         throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
 240                                 }
 241
 242                                 // Theoretically should be case-sensitive, but in practise...
 243                                 $keyword = strtolower( $keyword );
 244                                 if ( !isset( self::$textChunks[$keyword] ) ) {
 245                                         // Don't recognize chunk, so skip.
 246                                         fseek( $fh, self::$crcSize, SEEK_CUR );
 247                                         continue;
 248                                 }
 249                                 MediaWiki\suppressWarnings();
 250                                 $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
 251                                 MediaWiki\restoreWarnings();
 252
 253                                 if ( $content === false ) {
 254                                         throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
 255                                 }
 256
 257                                 $finalKeyword = self::$textChunks[$keyword];
 258                                 $text[$finalKeyword]['x-default'] = $content;
 259                                 $text[$finalKeyword]['_type'] = 'lang';
 260                         } elseif ( $chunk_type == 'zTXt' ) {
 261                                 if ( function_exists( 'gzuncompress' ) ) {
 262                                         $buf = self::read( $fh, $chunk_size );
 263
 264                                         // In case there is no \x00 which will make explode fail.
 265                                         if ( strpos( $buf, "\x00" ) === false ) {
 266                                                 throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
 267                                         }
 268
 269                                         list( $keyword, $postKeyword ) = explode( "\x00", $buf, 2 );
 270                                         if ( $keyword === '' || $postKeyword === '' ) {
 271                                                 throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
 272                                         }
 273                                         // Theoretically should be case-sensitive, but in practise...
 274                                         $keyword = strtolower( $keyword );
 275
 276                                         if ( !isset( self::$textChunks[$keyword] ) ) {
 277                                                 // Don't recognize chunk, so skip.
 278                                                 fseek( $fh, self::$crcSize, SEEK_CUR );
 279                                                 continue;
 280                                         }
 281                                         $compression = substr( $postKeyword, 0, 1 );
 282                                         $content = substr( $postKeyword, 1 );
 283                                         if ( $compression !== "\x00" ) {
 284                                                 wfDebug( __METHOD__ . " Unrecognized compression method in zTXt ($keyword). Skipping.\n" );
 285                                                 fseek( $fh, self::$crcSize, SEEK_CUR );
 286                                                 continue;
 287                                         }
 288
 289                                         MediaWiki\suppressWarnings();
 290                                         $content = gzuncompress( $content );
 291                                         MediaWiki\restoreWarnings();
 292
 293                                         if ( $content === false ) {
 294                                                 // decompression failed
 295                                                 wfDebug( __METHOD__ . ' Error decompressing zTXt chunk - ' . $keyword . "\n" );
 296                                                 fseek( $fh, self::$crcSize, SEEK_CUR );
 297                                                 continue;
 298                                         }
 299
 300                                         MediaWiki\suppressWarnings();
 301                                         $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
 302                                         MediaWiki\restoreWarnings();
 303
 304                                         if ( $content === false ) {
 305                                                 throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
 306                                         }
 307
 308                                         $finalKeyword = self::$textChunks[$keyword];
 309                                         $text[$finalKeyword]['x-default'] = $content;
 310                                         $text[$finalKeyword]['_type'] = 'lang';
 311                                 } else {
 312                                         wfDebug( __METHOD__ . " Cannot decompress zTXt chunk due to lack of zlib. Skipping.\n" );
 313                                         fseek( $fh, $chunk_size, SEEK_CUR );
 314                                 }
 315                         } elseif ( $chunk_type == 'tIME' ) {
 316                                 // last mod timestamp.
 317                                 if ( $chunk_size !== 7 ) {
 318                                         throw new Exception( __METHOD__ . ": tIME wrong size" );
 319                                 }
 320                                 $buf = self::read( $fh, $chunk_size );
 321                                 if ( !$buf || strlen( $buf ) < $chunk_size ) {
 322                                         throw new Exception( __METHOD__ . ": Read error" );
 323                                 }
 324
 325                                 // Note: spec says this should be UTC.
 326                                 $t = unpack( "ny/Cm/Cd/Ch/Cmin/Cs", $buf );
 327                                 $strTime = sprintf( "%04d%02d%02d%02d%02d%02d",
 328                                         $t['y'], $t['m'], $t['d'], $t['h'],
 329                                         $t['min'], $t['s'] );
 330
 331                                 $exifTime = wfTimestamp( TS_EXIF, $strTime );
 332
 333                                 if ( $exifTime ) {
 334                                         $text['DateTime'] = $exifTime;
 335                                 }
 336                         } elseif ( $chunk_type == 'pHYs' ) {
 337                                 // how big pixels are (dots per meter).
 338                                 if ( $chunk_size !== 9 ) {
 339                                         throw new Exception( __METHOD__ . ": pHYs wrong size" );
 340                                 }
 341
 342                                 $buf = self::read( $fh, $chunk_size );
 343                                 if ( !$buf || strlen( $buf ) < $chunk_size ) {
 344                                         throw new Exception( __METHOD__ . ": Read error" );
 345                                 }
 346
 347                                 $dim = unpack( "Nwidth/Nheight/Cunit", $buf );
 348                                 if ( $dim['unit'] == 1 ) {
 349                                         // Need to check for negative because php
 350                                         // doesn't deal with super-large unsigned 32-bit ints well
 351                                         if ( $dim['width'] > 0 && $dim['height'] > 0 ) {
 352                                                 // unit is meters
 353                                                 // (as opposed to 0 = undefined )
 354                                                 $text['XResolution'] = $dim['width']
 355                                                         . '/100';
 356                                                 $text['YResolution'] = $dim['height']
 357                                                         . '/100';
 358                                                 $text['ResolutionUnit'] = 3;
 359                                                 // 3 = dots per cm (from Exif).
 360                                         }
 361                                 }
 362                         } elseif ( $chunk_type == "IEND" ) {
 363                                 break;
 364                         } else {
 365                                 fseek( $fh, $chunk_size, SEEK_CUR );
 366                         }
 367                         fseek( $fh, self::$crcSize, SEEK_CUR );
 368                 }
 369                 fclose( $fh );
 370
 371                 if ( $loopCount > 1 ) {
 372                         $duration *= $loopCount;
 373                 }
 374
 375                 if ( isset( $text['DateTimeDigitized'] ) ) {
 376                         // Convert date format from rfc2822 to exif.
 377                         foreach ( $text['DateTimeDigitized'] as $name => &$value ) {
 378                                 if ( $name === '_type' ) {
 379                                         continue;
 380                                 }
 381
 382                                 // @todo FIXME: Currently timezones are ignored.
 383                                 // possibly should be wfTimestamp's
 384                                 // responsibility. (at least for numeric TZ)
 385                                 $formatted = wfTimestamp( TS_EXIF, $value );
 386                                 if ( $formatted ) {
 387                                         // Only change if we could convert the
 388                                         // date.
 389                                         // The png standard says it should be
 390                                         // in rfc2822 format, but not required.
 391                                         // In general for the exif stuff we
 392                                         // prettify the date if we can, but we
 393                                         // display as-is if we cannot or if
 394                                         // it is invalid.
 395                                         // So do the same here.
 396
 397                                         $value = $formatted;
 398                                 }
 399                         }
 400                 }
 401
 402                 return [
 403                         'frameCount' => $frameCount,
 404                         'loopCount' => $loopCount,
 405                         'duration' => $duration,
 406                         'text' => $text,
 407                         'bitDepth' => $bitDepth,
 408                         'colorType' => $colorType,
 409                 ];
 410         }
 411
 412         /**
 413          * Read a chunk, checking to make sure its not too big.
 414          *
 415          * @param resource $fh The file handle
 416          * @param int $size Size in bytes.
 417          * @throws Exception If too big
 418          * @return string The chunk.
 419          */
 420         private static function read( $fh, $size ) {
 421                 if ( $size > self::MAX_CHUNK_SIZE ) {
 422                         throw new Exception( __METHOD__ . ': Chunk size of ' . $size .
 423                                 ' too big. Max size is: ' . self::MAX_CHUNK_SIZE );
 424                 }
 425
 426                 return fread( $fh, $size );
 427         }
 428 }