public function flip($mode = self :: FLIP_HORIZONTAL) {
		
		if(false === in_array($mode, [self :: FLIP_HORIZONTAL, self :: FLIP_VERTICAL, self :: FLIP_BOTH])) {
			return trigger_error(sprintf('Unknown mode passed %s(), "%s" given', __METHOD__, gettype($mode)), E_USER_ERROR);
		}

		$this -> add(__FUNCTION__, func_get_args());
		return $this;
	}