colorm.go
func RotateHue(theta float64) ColorM {
	c := ColorM{}
	c.RotateHue(theta)
	return c
}
func RotateHue(theta float64) ColorM {
	c := ColorM{}
	c.RotateHue(theta)
	return c
}
// RotateHue is deprecated as of 1.2.0-alpha. Use RotateHue member function instead.