Helper function for _color_hsl2rgb().
function _color_hue2rgb($m1, $m2, $h) {
$h = $h < 0 ? $h + 1 : ($h > 1 ? $h - 1 : $h);
if ($h * 6 < 1) {
return $m1 + ($m2 - $m1) * $h * 6;
}
if ($h * 2 < 1) {
return $m2;
}
if ($h * 3 < 2) {
return $m1 + ($m2 - $m1) * (0.66666 - $h) * 6;
}
return $m1;
}