[bpt/emacs.git] / lisp / gnus / color-lab.el

;;; color-lab.el --- Color manipulation laboratory routines -*- coding: utf-8; -*-

;; Copyright (C) 2010 Free Software Foundation, Inc.

;; Author: Julien Danjou <julien@danjou.info>
;; Keywords: html

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This package provides color manipulation functions.

;;; Code:

(eval-when-compile
  (require 'cl))

;; Emacs < 23.3
(eval-and-compile
  (unless (boundp 'float-pi)
    (defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))

(defun rgb->hsv (red green blue)
  "Convert RED GREEN BLUE values to HSV representation.
Hue is in radian. Saturation and values are between 0 and 1."
   (let* ((r (float red))
	 (g (float green))
	 (b (float blue))
	 (max (max r g b))
	 (min (min r g b)))
     (list
      (/ (* 2 float-pi
            (cond ((and (= r g) (= g b)) 0)
                  ((and (= r max)
                        (>= g b))
                   (* 60 (/ (- g b) (- max min))))
                  ((and (= r max)
                        (< g b))
                   (+ 360 (* 60 (/ (- g b) (- max min)))))
                  ((= max g)
                   (+ 120 (* 60 (/ (- b r) (- max min)))))
                  ((= max b)
                       (+ 240 (* 60 (/ (- r g) (- max min)))))))
         360)
      (if (= max 0)
          0
        (- 1 (/ min max)))
      (/ max 255.0))))

(defun rgb->hsl (red green blue)
  "Convert RED GREEN BLUE colors to their HSL representation.
RED, GREEN and BLUE must be between 0 and 255."
  (let* ((r (/ red 255.0))
         (g (/ green 255.0))
         (b (/ blue 255.0))
         (max (max r g b))
         (min (min r g b))
         (delta (- max min))
         (l (/ (+ max min) 2.0)))
    (list
     (if (= max min)
         0
       (* 2 float-pi
          (/ (cond ((= max r)
                    (+ (/ (- g b) delta) (if (< g b) 6 0)))
                   ((= max g)
                 (+ (/ (- b r) delta) 2))
                   (t
                    (+ (/ (- r g) delta) 4)))
             6)))
     (if (= max min)
         0
       (if (> l 0.5)
           (/ delta (- 2 (+ max min)))
         (/ delta (+ max min))))
     l)))

(defun rgb->xyz (red green blue)
  "Converts RED GREEN BLUE colors to CIE XYZ representation.
RED, BLUE and GREEN must be between 0 and 1."
  (let ((r (if (<= red 0.04045)
               (/ red 12.95)
             (expt (/ (+ red 0.055) 1.055) 2.4)))
        (g (if (<= green 0.04045)
               (/ green 12.95)
             (expt (/ (+ green 0.055) 1.055) 2.4)))
        (b (if (<= blue 0.04045)
               (/ blue 12.95)
             (expt (/ (+ blue 0.055) 1.055) 2.4))))
    (list (+ (* 0.4124564 r) (* 0.3575761 g) (* 0.1804375 b))
          (+ (* 0.21266729 r) (* 0.7151522 g) (* 0.0721750 b))
          (+ (* 0.0193339 r) (* 0.1191920 g) (* 0.9503041 b)))))

(defun xyz->rgb (X Y Z)
  "Converts CIE XYZ colors to RGB."
  (let ((r (+ (* 3.2404542 X) (* -1.5371385 Y) (* -0.4985314 Z)))
        (g (+ (* -0.9692660 X) (* 1.8760108 Y) (* 0.0415560 Z)))
        (b (+ (* 0.0556434 X) (* -0.2040259 Y) (* 1.0572252 Z))))
    (list (if (<= r 0.0031308)
              (* 12.92 r)
            (- (* 1.055 (expt r (/ 1 2.4))) 0.055))
          (if (<= g 0.0031308)
              (* 12.92 g)
            (- (* 1.055 (expt g (/ 1 2.4))) 0.055))
          (if (<= b 0.0031308)
              (* 12.92 b)
            (- (* 1.055 (expt b (/ 1 2.4))) 0.055)))))

(defconst color-lab-d65-xyz '(0.950455 1.0 1.088753)
  "D65 white point in CIE XYZ.")

(defconst color-lab-ε (/ 216 24389.0))
(defconst color-lab-κ (/ 24389 27.0))

(defun xyz->lab (X Y Z &optional white-point)
  "Converts CIE XYZ to CIE L*a*b*.
WHITE-POINT can be specified as (X Y Z) white point to use. If
none is set, `color-lab-d65-xyz' is used."
  (destructuring-bind (Xr Yr Zr) (or white-point color-lab-d65-xyz)
      (let* ((xr (/ X Xr))
             (yr (/ Y Yr))
             (zr (/ Z Zr))
             (fx (if (> xr color-lab-ε)
                     (expt xr (/ 1 3.0))
                   (/ (+ (* color-lab-κ xr) 16) 116.0)))
             (fy (if (> yr color-lab-ε)
                     (expt yr (/ 1 3.0))
                   (/ (+ (* color-lab-κ yr) 16) 116.0)))
             (fz (if (> zr color-lab-ε)
                     (expt zr (/ 1 3.0))
                   (/ (+ (* color-lab-κ zr) 16) 116.0))))
        (list
         (- (* 116 fy) 16)                  ; L
         (* 500 (- fx fy))                  ; a
         (* 200 (- fy fz))))))              ; b

(defun lab->xyz (L a b &optional white-point)
  "Converts CIE L*a*b* to CIE XYZ.
WHITE-POINT can be specified as (X Y Z) white point to use. If
none is set, `color-lab-d65-xyz' is used."
  (destructuring-bind (Xr Yr Zr) (or white-point color-lab-d65-xyz)
      (let* ((fy (/ (+ L 16) 116.0))
             (fz (- fy (/ b 200.0)))
             (fx (+ (/ a 500.0) fy))
             (xr (if (> (expt fx 3.0) color-lab-ε)
                     (expt fx 3.0)
               (/ (- (* fx 116) 16) color-lab-κ)))
             (yr (if (> L (* color-lab-κ color-lab-ε))
                     (expt (/ (+ L 16) 116.0) 3.0)
                   (/ L color-lab-κ)))
             (zr (if (> (expt fz 3) color-lab-ε)
                     (expt fz 3.0)
                   (/ (- (* 116 fz) 16) color-lab-κ))))
        (list (* xr Xr)                 ; X
              (* yr Yr)                 ; Y
              (* zr Zr)))))             ; Z

(defun rgb->lab (red green blue)
  "Converts RGB to CIE L*a*b*."
  (apply 'xyz->lab (rgb->xyz red green blue)))

(defun rgb->normalize (color)
  "Normalize a RGB color to values between [0,1]."
  (mapcar (lambda (x) (/ x 65535.0)) (x-color-values color)))

(defun lab->rgb (L a b)
  "Converts CIE L*a*b* to RGB."
  (apply 'xyz->rgb (lab->xyz L a b)))

(defun color-lab-ciede2000 (color1 color2 &optional kL kC kH)
  "Computes the CIEDE2000 color distance between COLOR1 and COLOR2.
Colors must be in CIE L*a*b* format."
  (destructuring-bind (L₁ a₁ b₁) color1
    (destructuring-bind (L₂ a₂ b₂) color2
      (let* ((kL (or kL 1))
             (kC (or kC 1))
             (kH (or kH 1))
             (C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
             (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
             (C̄ (/ (+ C₁ C₂) 2.0))
             (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0) (+ (expt C̄ 7.0) (expt 25 7.0)))))))
             (a′₁ (* (+ 1 G) a₁))
             (a′₂ (* (+ 1 G) a₂))
             (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
             (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
             (h′₁ (if (and (= b₁ 0) (= a′₁ 0))
                      0
                    (let ((v (atan b₁ a′₁)))
                      (if (< v 0)
                          (+ v (* 2 float-pi))
                        v))))
             (h′₂ (if (and (= b₂ 0) (= a′₂ 0))
                      0
                    (let ((v (atan b₂ a′₂)))
                      (if (< v 0)
                          (+ v (* 2 float-pi))
                        v))))
             (ΔL′ (- L₂ L₁))
             (ΔC′ (- C′₂ C′₁))
             (Δh′ (cond ((= (* C′₁ C′₂) 0)
                         0)
                        ((<= (abs (- h′₂ h′₁)) float-pi)
                         (- h′₂ h′₁))
                        ((> (- h′₂ h′₁) float-pi)
                         (- (- h′₂ h′₁) (* 2 float-pi)))
                        ((< (- h′₂ h′₁) (- float-pi))
                         (+ (- h′₂ h′₁) (* 2 float-pi)))))
             (ΔH′ (* 2 (sqrt (* C′₁ C′₂)) (sin (/ Δh′ 2.0))))
             (L̄′ (/ (+ L₁ L₂) 2.0))
             (C̄′ (/ (+ C′₁ C′₂) 2.0))
             (h̄′ (cond ((= (* C′₁ C′₂) 0)
                        (+ h′₁ h′₂))
                       ((<= (abs (- h′₁ h′₂)) float-pi)
                        (/ (+ h′₁ h′₂) 2.0))
                       ((< (+ h′₁ h′₂) (* 2 float-pi))
                        (/ (+ h′₁ h′₂ (* 2 float-pi)) 2.0))
                       ((>= (+ h′₁ h′₂) (* 2 float-pi))
                        (/ (+ h′₁ h′₂ (* -2 float-pi)) 2.0))))
             (T (+ 1
                   (- (* 0.17 (cos (- h̄′ (degrees-to-radians 30)))))
                   (* 0.24 (cos (* h̄′ 2)))
                   (* 0.32 (cos (+ (* h̄′ 3) (degrees-to-radians 6))))
                   (- (* 0.20 (cos (- (* h̄′ 4) (degrees-to-radians 63)))))))
             (Δθ (* (degrees-to-radians 30) (exp (- (expt (/ (- h̄′ (degrees-to-radians 275)) (degrees-to-radians 25)) 2.0)))))
             (Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
             (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0)) (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
             (Sc (+ 1 (* C̄′ 0.045)))
             (Sh (+ 1 (* 0.015 C̄′ T)))
             (Rt (- (* (sin (* Δθ 2)) Rc))))
        (sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
                 (expt (/ ΔC′ (* Sc kC)) 2.0)
                 (expt (/ ΔH′ (* Sh kH)) 2.0)
                 (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))))

(provide 'color-lab)

;;; color-lab.el ends here
Commit	Line	Data
463bcf11	1	;;; color-lab.el --- Color manipulation laboratory routines -- coding: utf-8; --
ef6a2907 JD	2
	3	;; Copyright (C) 2010 Free Software Foundation, Inc.
	4
	5	;; Author: Julien Danjou <julien@danjou.info>
	6	;; Keywords: html
	7
	8	;; This file is part of GNU Emacs.
	9
	10	;; GNU Emacs is free software: you can redistribute it and/or modify
	11	;; it under the terms of the GNU General Public License as published by
	12	;; the Free Software Foundation, either version 3 of the License, or
	13	;; (at your option) any later version.
	14
	15	;; GNU Emacs is distributed in the hope that it will be useful,
	16	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	17	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	18	;; GNU General Public License for more details.
	19
	20	;; You should have received a copy of the GNU General Public License
	21	;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
	22
	23	;;; Commentary:
	24
	25	;; This package provides color manipulation functions.
	26
	27	;;; Code:
	28
5b42dfdd JD	29	(eval-when-compile
	30	(require 'cl))
	31
094ae2ab	32	;; Emacs < 23.3
463bcf11 KY	33	(eval-and-compile
	34	(unless (boundp 'float-pi)
	35	(defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))
094ae2ab	36
ef6a2907 JD	37	(defun rgb->hsv (red green blue)
	38	"Convert RED GREEN BLUE values to HSV representation.
	39	Hue is in radian. Saturation and values are between 0 and 1."
	40	(let* ((r (float red))
	41	(g (float green))
	42	(b (float blue))
	43	(max (max r g b))
	44	(min (min r g b)))
	45	(list
	46	(/ (* 2 float-pi
	47	(cond ((and (= r g) (= g b)) 0)
	48	((and (= r max)
	49	(>= g b))
	50	(* 60 (/ (- g b) (- max min))))
	51	((and (= r max)
	52	(< g b))
	53	(+ 360 (* 60 (/ (- g b) (- max min)))))
	54	((= max g)
	55	(+ 120 (* 60 (/ (- b r) (- max min)))))
	56	((= max b)
	57	(+ 240 (* 60 (/ (- r g) (- max min)))))))
	58	360)
	59	(if (= max 0)
	60	0
	61	(- 1 (/ min max)))
	62	(/ max 255.0))))
	63
	64	(defun rgb->hsl (red green blue)
	65	"Convert RED GREEN BLUE colors to their HSL representation.
	66	RED, GREEN and BLUE must be between 0 and 255."
	67	(let* ((r (/ red 255.0))
	68	(g (/ green 255.0))
	69	(b (/ blue 255.0))
	70	(max (max r g b))
	71	(min (min r g b))
	72	(delta (- max min))
	73	(l (/ (+ max min) 2.0)))
	74	(list
	75	(if (= max min)
	76	0
	77	(* 2 float-pi
	78	(/ (cond ((= max r)
	79	(+ (/ (- g b) delta) (if (< g b) 6 0)))
	80	((= max g)
	81	(+ (/ (- b r) delta) 2))
	82	(t
	83	(+ (/ (- r g) delta) 4)))
	84	6)))
	85	(if (= max min)
	86	0
	87	(if (> l 0.5)
	88	(/ delta (- 2 (+ max min)))
	89	(/ delta (+ max min))))
	90	l)))
	91
	92	(defun rgb->xyz (red green blue)
	93	"Converts RED GREEN BLUE colors to CIE XYZ representation.
	94	RED, BLUE and GREEN must be between 0 and 1."
	95	(let ((r (if (<= red 0.04045)
	96	(/ red 12.95)
	97	(expt (/ (+ red 0.055) 1.055) 2.4)))
	98	(g (if (<= green 0.04045)
	99	(/ green 12.95)
	100	(expt (/ (+ green 0.055) 1.055) 2.4)))
101	(b (if (<= blue 0.04045)
102	(/ blue 12.95)
103	(expt (/ (+ blue 0.055) 1.055) 2.4))))
104	(list (+ (* 0.4124564 r) (* 0.3575761 g) (* 0.1804375 b))
105	(+ (* 0.21266729 r) (* 0.7151522 g) (* 0.0721750 b))
106	(+ (* 0.0193339 r) (* 0.1191920 g) (* 0.9503041 b)))))
107
108	(defun xyz->rgb (X Y Z)
109	"Converts CIE XYZ colors to RGB."
110	(let ((r (+ (* 3.2404542 X) (* -1.5371385 Y) (* -0.4985314 Z)))
111	(g (+ (* -0.9692660 X) (* 1.8760108 Y) (* 0.0415560 Z)))
112	(b (+ (* 0.0556434 X) (* -0.2040259 Y) (* 1.0572252 Z))))
113	(list (if (<= r 0.0031308)
114	(* 12.92 r)
115	(- (* 1.055 (expt r (/ 1 2.4))) 0.055))
116	(if (<= g 0.0031308)
117	(* 12.92 g)
118	(- (* 1.055 (expt g (/ 1 2.4))) 0.055))
119	(if (<= b 0.0031308)
120	(* 12.92 b)
121	(- (* 1.055 (expt b (/ 1 2.4))) 0.055)))))
122
123	(defconst color-lab-d65-xyz '(0.950455 1.0 1.088753)
124	"D65 white point in CIE XYZ.")
125
126	(defconst color-lab-ε (/ 216 24389.0))
127	(defconst color-lab-κ (/ 24389 27.0))
128
129	(defun xyz->lab (X Y Z &optional white-point)
130	"Converts CIE XYZ to CIE Lab*.
131	WHITE-POINT can be specified as (X Y Z) white point to use. If
132	none is set, `color-lab-d65-xyz' is used."
133	(destructuring-bind (Xr Yr Zr) (or white-point color-lab-d65-xyz)
134	(let* ((xr (/ X Xr))
135	(yr (/ Y Yr))
136	(zr (/ Z Zr))
137	(fx (if (> xr color-lab-ε)
138	(expt xr (/ 1 3.0))
139	(/ (+ (* color-lab-κ xr) 16) 116.0)))
140	(fy (if (> yr color-lab-ε)
141	(expt yr (/ 1 3.0))
142	(/ (+ (* color-lab-κ yr) 16) 116.0)))
143	(fz (if (> zr color-lab-ε)
144	(expt zr (/ 1 3.0))
145	(/ (+ (* color-lab-κ zr) 16) 116.0))))
146	(list
147	(- (* 116 fy) 16) ; L
148	(* 500 (- fx fy)) ; a
149	(* 200 (- fy fz)))))) ; b
150
151	(defun lab->xyz (L a b &optional white-point)
152	"Converts CIE Lab* to CIE XYZ.
153	WHITE-POINT can be specified as (X Y Z) white point to use. If
154	none is set, `color-lab-d65-xyz' is used."
155	(destructuring-bind (Xr Yr Zr) (or white-point color-lab-d65-xyz)
156	(let* ((fy (/ (+ L 16) 116.0))
157	(fz (- fy (/ b 200.0)))
158	(fx (+ (/ a 500.0) fy))
67d43a1d G	159	(xr (if (> (expt fx 3.0) color-lab-ε)
67d43a1d G	160	(expt fx 3.0)
ef6a2907 JD	161	(/ (- (* fx 116) 16) color-lab-κ)))
ef6a2907 JD	162	(yr (if (> L (* color-lab-κ color-lab-ε))
67d43a1d	163	(expt (/ (+ L 16) 116.0) 3.0)
ef6a2907 JD	164	(/ L color-lab-κ)))
ef6a2907 JD	165	(zr (if (> (expt fz 3) color-lab-ε)
67d43a1d	166	(expt fz 3.0)
ef6a2907 JD	167	(/ (- (* 116 fz) 16) color-lab-κ))))
	168	(list (* xr Xr) ; X
	169	(* yr Yr) ; Y
	170	(* zr Zr))))) ; Z
	171
	172	(defun rgb->lab (red green blue)
	173	"Converts RGB to CIE Lab*."
	174	(apply 'xyz->lab (rgb->xyz red green blue)))
	175
	176	(defun rgb->normalize (color)
	177	"Normalize a RGB color to values between [0,1]."
	178	(mapcar (lambda (x) (/ x 65535.0)) (x-color-values color)))
	179
	180	(defun lab->rgb (L a b)
	181	"Converts CIE Lab* to RGB."
	182	(apply 'xyz->rgb (lab->xyz L a b)))
	183
	184	(defun color-lab-ciede2000 (color1 color2 &optional kL kC kH)
	185	"Computes the CIEDE2000 color distance between COLOR1 and COLOR2.
	186	Colors must be in CIE Lab* format."
	187	(destructuring-bind (L₁ a₁ b₁) color1
	188	(destructuring-bind (L₂ a₂ b₂) color2
	189	(let* ((kL (or kL 1))
	190	(kC (or kC 1))
	191	(kH (or kH 1))
67d43a1d G	192	(C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
67d43a1d G	193	(C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
ef6a2907	194	(C̄ (/ (+ C₁ C₂) 2.0))
67d43a1d	195	(G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0) (+ (expt C̄ 7.0) (expt 25 7.0)))))))
ef6a2907 JD	196	(a′₁ (* (+ 1 G) a₁))
ef6a2907 JD	197	(a′₂ (* (+ 1 G) a₂))
67d43a1d G	198	(C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
67d43a1d G	199	(C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
ef6a2907 JD	200	(h′₁ (if (and (= b₁ 0) (= a′₁ 0))
	201	0
	202	(let ((v (atan b₁ a′₁)))
	203	(if (< v 0)
	204	(+ v (* 2 float-pi))
	205	v))))
	206	(h′₂ (if (and (= b₂ 0) (= a′₂ 0))
	207	0
	208	(let ((v (atan b₂ a′₂)))
	209	(if (< v 0)
	210	(+ v (* 2 float-pi))
	211	v))))
	212	(ΔL′ (- L₂ L₁))
	213	(ΔC′ (- C′₂ C′₁))
	214	(Δh′ (cond ((= (* C′₁ C′₂) 0)
	215	0)
	216	((<= (abs (- h′₂ h′₁)) float-pi)
	217	(- h′₂ h′₁))
	218	((> (- h′₂ h′₁) float-pi)
	219	(- (- h′₂ h′₁) (* 2 float-pi)))
	220	((< (- h′₂ h′₁) (- float-pi))
	221	(+ (- h′₂ h′₁) (* 2 float-pi)))))
	222	(ΔH′ (* 2 (sqrt (* C′₁ C′₂)) (sin (/ Δh′ 2.0))))
	223	(L̄′ (/ (+ L₁ L₂) 2.0))
	224	(C̄′ (/ (+ C′₁ C′₂) 2.0))
	225	(h̄′ (cond ((= (* C′₁ C′₂) 0)
	226	(+ h′₁ h′₂))
	227	((<= (abs (- h′₁ h′₂)) float-pi)
	228	(/ (+ h′₁ h′₂) 2.0))
	229	((< (+ h′₁ h′₂) (* 2 float-pi))
	230	(/ (+ h′₁ h′₂ (* 2 float-pi)) 2.0))
	231	((>= (+ h′₁ h′₂) (* 2 float-pi))
	232	(/ (+ h′₁ h′₂ (* -2 float-pi)) 2.0))))
	233	(T (+ 1
	234	(- (* 0.17 (cos (- h̄′ (degrees-to-radians 30)))))
	235	(* 0.24 (cos (* h̄′ 2)))
	236	(* 0.32 (cos (+ (* h̄′ 3) (degrees-to-radians 6))))
	237	(- (* 0.20 (cos (- (* h̄′ 4) (degrees-to-radians 63)))))))
67d43a1d G	238	(Δθ (* (degrees-to-radians 30) (exp (- (expt (/ (- h̄′ (degrees-to-radians 275)) (degrees-to-radians 25)) 2.0)))))
	239	(Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
	240	(Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0)) (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
ef6a2907 JD	241	(Sc (+ 1 (* C̄′ 0.045)))
	242	(Sh (+ 1 (* 0.015 C̄′ T)))
	243	(Rt (- (* (sin (* Δθ 2)) Rc))))
67d43a1d G	244	(sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
	245	(expt (/ ΔC′ (* Sc kC)) 2.0)
	246	(expt (/ ΔH′ (* Sh kH)) 2.0)
ef6a2907 JD	247	(* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))))
	248
	249	(provide 'color-lab)
463bcf11 KY	250
463bcf11 KY	251	;;; color-lab.el ends here