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
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