public function addCircle($x, $y, $size, $counterClockwise)
    {
        $sweepFlag = $counterClockwise ? '0' : '1';
        $radiusAsString = number_format($size / 2, 2, '.', '');

        $this->dataString .=
            'M'. number_format($x, 2, '.', '') .' '. 
                number_format($y + $size / 2, 2, '.', '').
            'a'. $radiusAsString .','. $radiusAsString .' 0 1,'. 
                $sweepFlag .' '. number_format($size, 2, '.', '') .',0'.
            'a'. $radiusAsString .','. $radiusAsString .' 0 1,'. 
                $sweepFlag .' '. number_format(-$size, 2, '.', '') .',0';
    }