protected function linearDownsize($input = 0, $format = 0)
    {
        $format = (int) $this->validUnit(4, $format);

        if ($this->input == 'si') {
            $div = [1, 10, 100, 1000, 1000000];
        } else {
            $div = [1, 12, 36, 7920, 63360];
        }

        return (float) $input * $div[$format];
    }