Using Brushes in PHP

<?// www  . j  a va2s .  c om
    $brush = imagecreate(100,100);

    $brushtrans = imagecolorallocate($brush, 0, 0, 0);
    imagecolortransparent($brush, $brushtrans);

    for ($k = 1; $k < 18; ++$k) {
            $color = imagecolorallocate($brush, 255, $k * 15, 0);
            imagefilledellipse($brush, $k * 5, $k * 5, 5, 5, $color);
    }

    imagepng($brush);
    imagedestroy($brush);
?>