1 ;;; color.el --- Color manipulation laboratory routines -*- coding: utf-8; -*-
3 ;; Copyright (C) 2010 Free Software Foundation, Inc.
5 ;; Author: Julien Danjou <julien@danjou.info>
8 ;; This file is part of GNU Emacs.
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.
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.
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/>.
25 ;; This package provides color manipulation functions.
34 (unless (boundp 'float-pi)
35 (defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))
37 (defun color-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))
47 (cond ((and (= r g) (= g b)) 0)
50 (* 60 (/ (- g b) (- max min))))
53 (+ 360 (* 60 (/ (- g b) (- max min)))))
55 (+ 120 (* 60 (/ (- b r) (- max min)))))
57 (+ 240 (* 60 (/ (- r g) (- max min)))))))
64 (defun color-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))
73 (l (/ (+ max min) 2.0)))
79 (+ (/ (- g b) delta) (if (< g b) 6 0)))
81 (+ (/ (- b r) delta) 2))
83 (+ (/ (- r g) delta) 4)))
88 (/ delta (- 2 (+ max min)))
89 (/ delta (+ max min))))
92 (defun color-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)
97 (expt (/ (+ red 0.055) 1.055) 2.4)))
98 (g (if (<= green 0.04045)
100 (expt (/ (+ green 0.055) 1.055) 2.4)))
101 (b (if (<= blue 0.04045)
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)))))
108 (defun color-xyz->rgb (X Y Z)
109 "Converts CIE X Y Z 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)
115 (- (* 1.055 (expt r (/ 1 2.4))) 0.055))
118 (- (* 1.055 (expt g (/ 1 2.4))) 0.055))
121 (- (* 1.055 (expt b (/ 1 2.4))) 0.055)))))
123 (defconst color-d65-xyz '(0.950455 1.0 1.088753)
124 "D65 white point in CIE XYZ.")
126 (defconst color-cie-ε (/ 216 24389.0))
127 (defconst color-cie-κ (/ 24389 27.0))
129 (defun color-xyz->lab (X Y Z &optional white-point)
130 "Converts CIE XYZ to CIE L*a*b*.
131 WHITE-POINT can be specified as (X Y Z) white point to use. If
132 none is set, `color-d65-xyz' is used."
133 (destructuring-bind (Xr Yr Zr) (or white-point color-d65-xyz)
137 (fx (if (> xr color-cie-ε)
139 (/ (+ (* color-cie-κ xr) 16) 116.0)))
140 (fy (if (> yr color-cie-ε)
142 (/ (+ (* color-cie-κ yr) 16) 116.0)))
143 (fz (if (> zr color-cie-ε)
145 (/ (+ (* color-cie-κ zr) 16) 116.0))))
147 (- (* 116 fy) 16) ; L
148 (* 500 (- fx fy)) ; a
149 (* 200 (- fy fz)))))) ; b
151 (defun color-lab->xyz (L a b &optional white-point)
152 "Converts CIE L*a*b* to CIE XYZ.
153 WHITE-POINT can be specified as (X Y Z) white point to use. If
154 none is set, `color-d65-xyz' is used."
155 (destructuring-bind (Xr Yr Zr) (or white-point color-d65-xyz)
156 (let* ((fy (/ (+ L 16) 116.0))
157 (fz (- fy (/ b 200.0)))
158 (fx (+ (/ a 500.0) fy))
159 (xr (if (> (expt fx 3.0) color-cie-ε)
161 (/ (- (* fx 116) 16) color-cie-κ)))
162 (yr (if (> L (* color-cie-κ color-cie-ε))
163 (expt (/ (+ L 16) 116.0) 3.0)
165 (zr (if (> (expt fz 3) color-cie-ε)
167 (/ (- (* 116 fz) 16) color-cie-κ))))
172 (defun color-rgb->lab (red green blue)
173 "Converts RGB to CIE L*a*b*."
174 (apply 'color-xyz->lab (color-rgb->xyz red green blue)))
176 (defun color-rgb->normalize (color)
177 "Normalize a RGB color to values between [0,1]."
178 (mapcar (lambda (x) (/ x 65535.0)) (x-color-values color)))
180 (defun color-lab->rgb (L a b)
181 "Converts CIE L*a*b* to RGB."
182 (apply 'color-xyz->rgb (color-lab->xyz L a b)))
184 (defun color-cie-de2000 (color1 color2 &optional kL kC kH)
185 "Computes the CIEDE2000 color distance between COLOR1 and COLOR2.
186 Colors must be in CIE L*a*b* format."
187 (destructuring-bind (L₁ a₁ b₁) color1
188 (destructuring-bind (L₂ a₂ b₂) color2
189 (let* ((kL (or kL 1))
192 (C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
193 (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
194 (C̄ (/ (+ C₁ C₂) 2.0))
195 (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0) (+ (expt C̄ 7.0) (expt 25 7.0)))))))
198 (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
199 (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
200 (h′₁ (if (and (= b₁ 0) (= a′₁ 0))
202 (let ((v (atan b₁ a′₁)))
206 (h′₂ (if (and (= b₂ 0) (= a′₂ 0))
208 (let ((v (atan b₂ a′₂)))
214 (Δh′ (cond ((= (* C′₁ C′₂) 0)
216 ((<= (abs (- h′₂ h′₁)) float-pi)
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)
227 ((<= (abs (- h′₁ h′₂)) float-pi)
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))))
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)))))))
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))))))
241 (Sc (+ 1 (* C̄′ 0.045)))
242 (Sh (+ 1 (* 0.015 C̄′ T)))
243 (Rt (- (* (sin (* Δθ 2)) Rc))))
244 (sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
245 (expt (/ ΔC′ (* Sc kC)) 2.0)
246 (expt (/ ΔH′ (* Sh kH)) 2.0)
247 (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))))
251 ;;; color.el ends here