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<?php
/**
* PNG frame counter.
* Slightly derived from GIFMetadataExtractor.php
* Deliberately not using MWExceptions to avoid external dependencies, encouraging
* redistribution.
*
* @file
* @ingroup Media
*/
/**
* PNG frame counter.
*
* @ingroup Media
*/
class PNGMetadataExtractor {
static $png_sig;
static $CRC_size;
static function getMetadata( $filename ) {
self::$png_sig = pack( "C8", 137, 80, 78, 71, 13, 10, 26, 10 );
self::$CRC_size = 4;
$frameCount = 0;
$loopCount = 1;
$duration = 0.0;
if (!$filename)
throw new Exception( __METHOD__ . ": No file name specified" );
elseif ( !file_exists($filename) || is_dir($filename) )
throw new Exception( __METHOD__ . ": File $filename does not exist" );
$fh = fopen( $filename, 'r' );
if (!$fh) {
throw new Exception( __METHOD__ . ": Unable to open file $filename" );
}
// Check for the PNG header
$buf = fread( $fh, 8 );
if ( $buf != self::$png_sig ) {
throw new Exception( __METHOD__ . ": Not a valid PNG file; header: $buf" );
}
// Read chunks
while( !feof( $fh ) ) {
$buf = fread( $fh, 4 );
if( !$buf ) {
throw new Exception( __METHOD__ . ": Read error" );
}
$chunk_size = unpack( "N", $buf);
$chunk_size = $chunk_size[1];
$chunk_type = fread( $fh, 4 );
if( !$chunk_type ) {
throw new Exception( __METHOD__ . ": Read error" );
}
if ( $chunk_type == "acTL" ) {
$buf = fread( $fh, $chunk_size );
if( !$buf ) {
throw new Exception( __METHOD__ . ": Read error" );
}
$actl = unpack( "Nframes/Nplays", $buf );
$frameCount = $actl['frames'];
$loopCount = $actl['plays'];
} elseif ( $chunk_type == "fcTL" ) {
$buf = fread( $fh, $chunk_size );
if( !$buf ) {
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'] ) {
$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 == "IEND" ) {
break;
} else {
fseek( $fh, $chunk_size, SEEK_CUR );
}
fseek( $fh, self::$CRC_size, SEEK_CUR );
}
fclose( $fh );
if( $loopCount > 1 ) {
$duration *= $loopCount;
}
return array(
'frameCount' => $frameCount,
'loopCount' => $loopCount,
'duration' => $duration
);
}
}
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