Convert from RGB to HSV (Emacs)

my-color-rgb-to-hsv.el

(defun my-color-rgb-to-hsv (r g b)
	"RGB[0.0, 1.0]からHSV[0.0, 1.0]へ変換する (SOURCE:Wikipedia)"
	(let* ((max (max r g b))
				 (min (min r g b))
				 (h (- max min))
				 (s (- max min))
				 (v max))
		(if (> h 0.0)
				(cond ((= max r)
							 (progn
								 (setq h (/ (- g b) h))
								 (if (< h 0.0)
										 (setq h (+ 6.0)))))
							((= max g)
							 (setq h (+ 2.0 (/ (- b r) h))))
							(t
							 (setq h (+ 4.0 (/ (- r g) h))))))
		(setq h (/ h 6.0))
		(if (/= max 0)
				(setq s (/ s max)))
		(list h s v)))