protected function extractSizeInfo($i)
	{
		// Extract size info from SOF marker
		list(, $unpacked) = unpack("H*", substr($this->data, $i - 1 + self::LONG_SIZE, self::LONG_SIZE));

		// Get width and height from unpacked size info
		$size = array(
			'width'		=> hexdec(substr($unpacked, 4, 4)),
			'height'	=> hexdec(substr($unpacked, 0, 4)),
		);

		return $size;
	}