--- /dev/null
+;;; color-lab.el --- Color manipulation laboratory routines
+
+;; 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:
+
+(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) color-lab-ε)
+ (expt fx 3)
+ (/ (- (* fx 116) 16) color-lab-κ)))
+ (yr (if (> L (* color-lab-κ color-lab-ε))
+ (expt (/ (+ L 16) 116.0) 3)
+ (/ L color-lab-κ)))
+ (zr (if (> (expt fz 3) color-lab-ε)
+ (expt fz 3)
+ (/ (- (* 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) (expt b₁ 2))))
+ (C₂ (sqrt (+ (expt a₂ 2) (expt b₂ 2))))
+ (C̄ (/ (+ C₁ C₂) 2.0))
+ (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7) (+ (expt C̄ 7) (expt 25 7)))))))
+ (a′₁ (* (+ 1 G) a₁))
+ (a′₂ (* (+ 1 G) a₂))
+ (C′₁ (sqrt (+ (expt a′₁ 2) (expt b₁ 2))))
+ (C′₂ (sqrt (+ (expt a′₂ 2) (expt b₂ 2))))
+ (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)))))
+ (Rc (* 2 (sqrt (/ (expt C̄′ 7) (+ (expt C̄′ 7) (expt 25 7))))))
+ (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2)) (sqrt (+ 20 (expt (- L̄′ 50) 2))))))
+ (Sc (+ 1 (* C̄′ 0.045)))
+ (Sh (+ 1 (* 0.015 C̄′ T)))
+ (Rt (- (* (sin (* Δθ 2)) Rc))))
+ (sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2)
+ (expt (/ ΔC′ (* Sc kC)) 2)
+ (expt (/ ΔH′ (* Sh kH)) 2)
+ (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))))
+
+(provide 'color-lab)
projects / gnus / commitdiff