protected function lib_invert($args)
{
$value = $args[0];
if ($value[0] === 'number') {
return null;
}
$color = $this->assertColor($value);
$color[1] = 255 - $color[1];
$color[2] = 255 - $color[2];
$color[3] = 255 - $color[3];
return $color;
}