[PATCH] color-hsv-to-rgb

[Dov Grobgeld <dov.grobgeld@gmail.com>]

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Hello.

I would like to do my first(!) contribution to emacs with the attached
patch. Is there interest, or is it too trivial? Do I need to do a copyright
assignment? Is there a guide for dummies on how to do that?

With hope for better times...

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diff --git a/lisp/color.el b/lisp/color.el
index f68cf5e6b17..37f11f23c7c 100644
--- a/lisp/color.el
+++ b/lisp/color.el
@@ -123,6 +123,26 @@ color-complement-hex
   "Return the color that is the complement of COLOR, in hexadecimal format."
   (apply 'color-rgb-to-hex (color-complement color)))
 
+(defun color-hsv-to-rgb (H S V)
+  "Convert hue, saturation and value to their RGB representation.
+H, S, and V should each be numbers between 0.0 and 1.0, inclusive.
+Return a list (RED GREEN BLUE), where each element is between 0.0 and 1.0,
+inclusive."
+  (let* ((I (floor (* 6 H)))
+         (F (- (* H 6) I))
+         (P (* V (- 1.0 S)))
+         (Q (* V (- 1.0 (* F S))))
+         (T (* V (- 1.0 (* (- 1.0 F) S))))
+         (I (mod I 6)))
+    (cond
+     ((= I 0) (list V T P))
+     ((= I 1) (list Q V P))
+     ((= I 2) (list P V T))
+     ((= I 3) (list P Q V))
+     ((= I 4) (list T P V))
+     ((= I 5) (list V P Q))
+     (t (list 0 0 0)))))
+
 (defun color-rgb-to-hsv (red green blue)
   "Convert RGB color components to HSV.
 RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,