<?php
/**
- * PNG frame counter.
+ * PNG frame counter and metadata extractor.
+ *
* Slightly derived from GIFMetadataExtractor.php
* Deliberately not using MWExceptions to avoid external dependencies, encouraging
* redistribution.
*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
* @file
* @ingroup Media
*/
* @ingroup Media
*/
class PNGMetadataExtractor {
- static $png_sig;
- static $CRC_size;
+ /** @var string */
+ private static $pngSig;
+
+ /** @var int */
+ private static $crcSize;
+
+ /** @var array */
+ private static $textChunks;
+
+ const VERSION = 1;
+ const MAX_CHUNK_SIZE = 3145728; // 3 megabytes
static function getMetadata( $filename ) {
- self::$png_sig = pack( "C8", 137, 80, 78, 71, 13, 10, 26, 10 );
- self::$CRC_size = 4;
-
+ self::$pngSig = pack( "C8", 137, 80, 78, 71, 13, 10, 26, 10 );
+ self::$crcSize = 4;
+ /* based on list at http://owl.phy.queensu.ca/~phil/exiftool/TagNames/PNG.html#TextualData
+ * and https://www.w3.org/TR/PNG/#11keywords
+ */
+ self::$textChunks = [
+ 'xml:com.adobe.xmp' => 'xmp',
+ # Artist is unofficial. Author is the recommended
+ # keyword in the PNG spec. However some people output
+ # Artist so support both.
+ 'artist' => 'Artist',
+ 'model' => 'Model',
+ 'make' => 'Make',
+ 'author' => 'Artist',
+ 'comment' => 'PNGFileComment',
+ 'description' => 'ImageDescription',
+ 'title' => 'ObjectName',
+ 'copyright' => 'Copyright',
+ # Source as in original device used to make image
+ # not as in who gave you the image
+ 'source' => 'Model',
+ 'software' => 'Software',
+ 'disclaimer' => 'Disclaimer',
+ 'warning' => 'ContentWarning',
+ 'url' => 'Identifier', # Not sure if this is best mapping. Maybe WebStatement.
+ 'label' => 'Label',
+ 'creation time' => 'DateTimeDigitized',
+ /* Other potentially useful things - Document */
+ ];
+
$frameCount = 0;
$loopCount = 1;
+ $text = [];
$duration = 0.0;
+ $bitDepth = 0;
+ $colorType = 'unknown';
- if (!$filename)
+ if ( !$filename ) {
throw new Exception( __METHOD__ . ": No file name specified" );
- elseif ( !file_exists($filename) || is_dir($filename) )
+ } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
throw new Exception( __METHOD__ . ": File $filename does not exist" );
-
- $fh = fopen( $filename, 'r' );
-
- if (!$fh) {
+ }
+
+ $fh = fopen( $filename, 'rb' );
+
+ if ( !$fh ) {
throw new Exception( __METHOD__ . ": Unable to open file $filename" );
}
-
+
// Check for the PNG header
$buf = fread( $fh, 8 );
- if ( $buf != self::$png_sig ) {
+ if ( $buf != self::$pngSig ) {
throw new Exception( __METHOD__ . ": Not a valid PNG file; header: $buf" );
}
// Read chunks
- while( !feof( $fh ) ) {
+ while ( !feof( $fh ) ) {
$buf = fread( $fh, 4 );
- if( !$buf ) {
+ if ( !$buf || strlen( $buf ) < 4 ) {
throw new Exception( __METHOD__ . ": Read error" );
}
- $chunk_size = unpack( "N", $buf);
- $chunk_size = $chunk_size[1];
+ $chunk_size = unpack( "N", $buf )[1];
+
+ if ( $chunk_size < 0 ) {
+ throw new Exception( __METHOD__ . ": Chunk size too big for unpack" );
+ }
$chunk_type = fread( $fh, 4 );
- if( !$chunk_type ) {
+ if ( !$chunk_type || strlen( $chunk_type ) < 4 ) {
throw new Exception( __METHOD__ . ": Read error" );
}
- if ( $chunk_type == "acTL" ) {
+ if ( $chunk_type == "IHDR" ) {
+ $buf = self::read( $fh, $chunk_size );
+ if ( !$buf || strlen( $buf ) < $chunk_size ) {
+ throw new Exception( __METHOD__ . ": Read error" );
+ }
+ $width = unpack( 'N', substr( $buf, 0, 4 ) )[1];
+ $height = unpack( 'N', substr( $buf, 4, 4 ) )[1];
+ $bitDepth = ord( substr( $buf, 8, 1 ) );
+ // Detect the color type in British English as per the spec
+ // https://www.w3.org/TR/PNG/#11IHDR
+ switch ( ord( substr( $buf, 9, 1 ) ) ) {
+ case 0:
+ $colorType = 'greyscale';
+ break;
+ case 2:
+ $colorType = 'truecolour';
+ break;
+ case 3:
+ $colorType = 'index-coloured';
+ break;
+ case 4:
+ $colorType = 'greyscale-alpha';
+ break;
+ case 6:
+ $colorType = 'truecolour-alpha';
+ break;
+ default:
+ $colorType = 'unknown';
+ break;
+ }
+ } elseif ( $chunk_type == "acTL" ) {
$buf = fread( $fh, $chunk_size );
- if( !$buf ) {
+ if ( !$buf || strlen( $buf ) < $chunk_size || $chunk_size < 4 ) {
throw new Exception( __METHOD__ . ": Read error" );
}
$frameCount = $actl['frames'];
$loopCount = $actl['plays'];
} elseif ( $chunk_type == "fcTL" ) {
- $buf = fread( $fh, $chunk_size );
- if( !$buf ) {
+ $buf = self::read( $fh, $chunk_size );
+ if ( !$buf || strlen( $buf ) < $chunk_size ) {
+ throw new Exception( __METHOD__ . ": Read error" );
+ }
+ $buf = substr( $buf, 20 );
+ if ( strlen( $buf ) < 4 ) {
throw new Exception( __METHOD__ . ": Read error" );
}
- $buf = substr( $buf, 20 );
$fctldur = unpack( "ndelay_num/ndelay_den", $buf );
- if( $fctldur['delay_den'] == 0 ) $fctldur['delay_den'] = 100;
- if( $fctldur['delay_num'] ) {
+ if ( $fctldur['delay_den'] == 0 ) {
+ $fctldur['delay_den'] = 100;
+ }
+ if ( $fctldur['delay_num'] ) {
$duration += $fctldur['delay_num'] / $fctldur['delay_den'];
}
- } elseif ( ( $chunk_type == "IDAT" || $chunk_type == "IEND" ) && $frameCount == 0 ) {
- // Not a valid animated image. No point in continuing.
- break;
+ } elseif ( $chunk_type == "iTXt" ) {
+ // Extracts iTXt chunks, uncompressing if necessary.
+ $buf = self::read( $fh, $chunk_size );
+ $items = [];
+ if ( preg_match(
+ '/^([^\x00]{1,79})\x00(\x00|\x01)\x00([^\x00]*)(.)[^\x00]*\x00(.*)$/Ds',
+ $buf, $items )
+ ) {
+ /* $items[1] = text chunk name, $items[2] = compressed flag,
+ * $items[3] = lang code (or ""), $items[4]= compression type.
+ * $items[5] = content
+ */
+
+ // Theoretically should be case-sensitive, but in practise...
+ $items[1] = strtolower( $items[1] );
+ if ( !isset( self::$textChunks[$items[1]] ) ) {
+ // Only extract textual chunks on our list.
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+
+ $items[3] = strtolower( $items[3] );
+ if ( $items[3] == '' ) {
+ // if no lang specified use x-default like in xmp.
+ $items[3] = 'x-default';
+ }
+
+ // if compressed
+ if ( $items[2] == "\x01" ) {
+ if ( function_exists( 'gzuncompress' ) && $items[4] === "\x00" ) {
+ MediaWiki\suppressWarnings();
+ $items[5] = gzuncompress( $items[5] );
+ MediaWiki\restoreWarnings();
+
+ if ( $items[5] === false ) {
+ // decompression failed
+ wfDebug( __METHOD__ . ' Error decompressing iTxt chunk - ' . $items[1] . "\n" );
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+ } else {
+ wfDebug( __METHOD__ . ' Skipping compressed png iTXt chunk due to lack of zlib,'
+ . " or potentially invalid compression method\n" );
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+ }
+ $finalKeyword = self::$textChunks[$items[1]];
+ $text[$finalKeyword][$items[3]] = $items[5];
+ $text[$finalKeyword]['_type'] = 'lang';
+ } else {
+ // Error reading iTXt chunk
+ throw new Exception( __METHOD__ . ": Read error on iTXt chunk" );
+ }
+ } elseif ( $chunk_type == 'tEXt' ) {
+ $buf = self::read( $fh, $chunk_size );
+
+ // In case there is no \x00 which will make explode fail.
+ if ( strpos( $buf, "\x00" ) === false ) {
+ throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
+ }
+
+ list( $keyword, $content ) = explode( "\x00", $buf, 2 );
+ if ( $keyword === '' || $content === '' ) {
+ throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
+ }
+
+ // Theoretically should be case-sensitive, but in practise...
+ $keyword = strtolower( $keyword );
+ if ( !isset( self::$textChunks[$keyword] ) ) {
+ // Don't recognize chunk, so skip.
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+ MediaWiki\suppressWarnings();
+ $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
+ MediaWiki\restoreWarnings();
+
+ if ( $content === false ) {
+ throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
+ }
+
+ $finalKeyword = self::$textChunks[$keyword];
+ $text[$finalKeyword]['x-default'] = $content;
+ $text[$finalKeyword]['_type'] = 'lang';
+ } elseif ( $chunk_type == 'zTXt' ) {
+ if ( function_exists( 'gzuncompress' ) ) {
+ $buf = self::read( $fh, $chunk_size );
+
+ // In case there is no \x00 which will make explode fail.
+ if ( strpos( $buf, "\x00" ) === false ) {
+ throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
+ }
+
+ list( $keyword, $postKeyword ) = explode( "\x00", $buf, 2 );
+ if ( $keyword === '' || $postKeyword === '' ) {
+ throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
+ }
+ // Theoretically should be case-sensitive, but in practise...
+ $keyword = strtolower( $keyword );
+
+ if ( !isset( self::$textChunks[$keyword] ) ) {
+ // Don't recognize chunk, so skip.
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+ $compression = substr( $postKeyword, 0, 1 );
+ $content = substr( $postKeyword, 1 );
+ if ( $compression !== "\x00" ) {
+ wfDebug( __METHOD__ . " Unrecognized compression method in zTXt ($keyword). Skipping.\n" );
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+
+ MediaWiki\suppressWarnings();
+ $content = gzuncompress( $content );
+ MediaWiki\restoreWarnings();
+
+ if ( $content === false ) {
+ // decompression failed
+ wfDebug( __METHOD__ . ' Error decompressing zTXt chunk - ' . $keyword . "\n" );
+ fseek( $fh, self::$crcSize, SEEK_CUR );
+ continue;
+ }
+
+ MediaWiki\suppressWarnings();
+ $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
+ MediaWiki\restoreWarnings();
+
+ if ( $content === false ) {
+ throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
+ }
+
+ $finalKeyword = self::$textChunks[$keyword];
+ $text[$finalKeyword]['x-default'] = $content;
+ $text[$finalKeyword]['_type'] = 'lang';
+ } else {
+ wfDebug( __METHOD__ . " Cannot decompress zTXt chunk due to lack of zlib. Skipping.\n" );
+ fseek( $fh, $chunk_size, SEEK_CUR );
+ }
+ } elseif ( $chunk_type == 'tIME' ) {
+ // last mod timestamp.
+ if ( $chunk_size !== 7 ) {
+ throw new Exception( __METHOD__ . ": tIME wrong size" );
+ }
+ $buf = self::read( $fh, $chunk_size );
+ if ( !$buf || strlen( $buf ) < $chunk_size ) {
+ throw new Exception( __METHOD__ . ": Read error" );
+ }
+
+ // Note: spec says this should be UTC.
+ $t = unpack( "ny/Cm/Cd/Ch/Cmin/Cs", $buf );
+ $strTime = sprintf( "%04d%02d%02d%02d%02d%02d",
+ $t['y'], $t['m'], $t['d'], $t['h'],
+ $t['min'], $t['s'] );
+
+ $exifTime = wfTimestamp( TS_EXIF, $strTime );
+
+ if ( $exifTime ) {
+ $text['DateTime'] = $exifTime;
+ }
+ } elseif ( $chunk_type == 'pHYs' ) {
+ // how big pixels are (dots per meter).
+ if ( $chunk_size !== 9 ) {
+ throw new Exception( __METHOD__ . ": pHYs wrong size" );
+ }
+
+ $buf = self::read( $fh, $chunk_size );
+ if ( !$buf || strlen( $buf ) < $chunk_size ) {
+ throw new Exception( __METHOD__ . ": Read error" );
+ }
+
+ $dim = unpack( "Nwidth/Nheight/Cunit", $buf );
+ if ( $dim['unit'] == 1 ) {
+ // Need to check for negative because php
+ // doesn't deal with super-large unsigned 32-bit ints well
+ if ( $dim['width'] > 0 && $dim['height'] > 0 ) {
+ // unit is meters
+ // (as opposed to 0 = undefined )
+ $text['XResolution'] = $dim['width']
+ . '/100';
+ $text['YResolution'] = $dim['height']
+ . '/100';
+ $text['ResolutionUnit'] = 3;
+ // 3 = dots per cm (from Exif).
+ }
+ }
} elseif ( $chunk_type == "IEND" ) {
break;
} else {
fseek( $fh, $chunk_size, SEEK_CUR );
}
- fseek( $fh, self::$CRC_size, SEEK_CUR );
+ fseek( $fh, self::$crcSize, SEEK_CUR );
}
fclose( $fh );
- if( $loopCount > 1 ) {
+ if ( $loopCount > 1 ) {
$duration *= $loopCount;
}
- return array(
+ if ( isset( $text['DateTimeDigitized'] ) ) {
+ // Convert date format from rfc2822 to exif.
+ foreach ( $text['DateTimeDigitized'] as $name => &$value ) {
+ if ( $name === '_type' ) {
+ continue;
+ }
+
+ // @todo FIXME: Currently timezones are ignored.
+ // possibly should be wfTimestamp's
+ // responsibility. (at least for numeric TZ)
+ $formatted = wfTimestamp( TS_EXIF, $value );
+ if ( $formatted ) {
+ // Only change if we could convert the
+ // date.
+ // The png standard says it should be
+ // in rfc2822 format, but not required.
+ // In general for the exif stuff we
+ // prettify the date if we can, but we
+ // display as-is if we cannot or if
+ // it is invalid.
+ // So do the same here.
+
+ $value = $formatted;
+ }
+ }
+ }
+
+ return [
'frameCount' => $frameCount,
'loopCount' => $loopCount,
- 'duration' => $duration
- );
-
+ 'duration' => $duration,
+ 'text' => $text,
+ 'bitDepth' => $bitDepth,
+ 'colorType' => $colorType,
+ ];
+ }
+
+ /**
+ * Read a chunk, checking to make sure its not too big.
+ *
+ * @param resource $fh The file handle
+ * @param int $size Size in bytes.
+ * @throws Exception If too big
+ * @return string The chunk.
+ */
+ private static function read( $fh, $size ) {
+ if ( $size > self::MAX_CHUNK_SIZE ) {
+ throw new Exception( __METHOD__ . ': Chunk size of ' . $size .
+ ' too big. Max size is: ' . self::MAX_CHUNK_SIZE );
+ }
+
+ return fread( $fh, $size );
}
}
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