lisp/color.el

   1 ;;; color.el --- Color manipulation library -*- coding: utf-8; lexical-binding:t -*-
   2
   3 ;; Copyright (C) 2010-2013 Free Software Foundation, Inc.
   4
   5 ;; Authors: Julien Danjou <julien@danjou.info>
   6 ;;          Drew Adams <drew.adams@oracle.com>
   7 ;; Keywords: lisp, faces, color, hex, rgb, hsv, hsl, cie-lab, background
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software: you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation, either version 3 of the License, or
  14 ;; (at your option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; This package provides functions for manipulating colors, including
  27 ;; converting between color representations, computing color
  28 ;; complements, and computing CIEDE2000 color distances.
  29 ;;
  30 ;; Supported color representations include RGB (red, green, blue), HSV
  31 ;; (hue, saturation, value), HSL (hue, saturation, luminance), sRGB,
  32 ;; CIE XYZ, and CIE L*a*b* color components.
  33
  34 ;;; Code:
  35
  36 (eval-when-compile
  37   (require 'cl))
  38
  39 ;; Emacs < 23.3
  40 (eval-and-compile
  41   (unless (boundp 'float-pi)
  42     (defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))
  43
  44 ;;;###autoload
  45 (defun color-name-to-rgb (color &optional frame)
  46   "Convert COLOR string to a list of normalized RGB components.
  47 COLOR should be a color name (e.g. \"white\") or an RGB triplet
  48 string (e.g. \"#ff12ec\").
  49
  50 Normally the return value is a list of three floating-point
  51 numbers, (RED GREEN BLUE), each between 0.0 and 1.0 inclusive.
  52
  53 Optional argument FRAME specifies the frame where the color is to be
  54 displayed.  If FRAME is omitted or nil, use the selected frame.
  55 If FRAME cannot display COLOR, return nil."
  56   ;; `colors-values' maximum value is either 65535 or 65280 depending on the
  57   ;; display system.  So we use a white conversion to get the max value.
  58   (let ((valmax (float (car (color-values "#ffffff")))))
  59     (mapcar (lambda (x) (/ x valmax)) (color-values color frame))))
  60
  61 (defun color-rgb-to-hex  (red green blue)
  62   "Return hexadecimal notation for the color RED GREEN BLUE.
  63 RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive."
  64   (format "#%02x%02x%02x"
  65           (* red 255) (* green 255) (* blue 255)))
  66
  67 (defun color-complement (color-name)
  68   "Return the color that is the complement of COLOR-NAME.
  69 COLOR-NAME should be a string naming a color (e.g. \"white\"), or
  70 a string specifying a color's RGB components (e.g. \"#ff12ec\")."
  71   (let ((color (color-name-to-rgb color-name)))
  72     (list (- 1.0 (car color))
  73           (- 1.0 (cadr color))
  74           (- 1.0 (caddr color)))))
  75
  76 (defun color-gradient (start stop step-number)
  77   "Return a list with STEP-NUMBER colors from START to STOP.
  78 The color list builds a color gradient starting at color START to
  79 color STOP.  It does not include the START and STOP color in the
  80 resulting list."
  81   (let* ((r (nth 0 start))
  82          (g (nth 1 start))
  83          (b (nth 2 start))
  84          (r-step (/ (- (nth 0 stop) r) (1+ step-number)))
  85          (g-step (/ (- (nth 1 stop) g) (1+ step-number)))
  86          (b-step (/ (- (nth 2 stop) b) (1+ step-number)))
  87          result)
  88     (dotimes (_ step-number)
  89       (push (list (setq r (+ r r-step))
  90                   (setq g (+ g g-step))
  91                   (setq b (+ b b-step)))
  92             result))
  93     (nreverse result)))
  94
  95 (defun color-hue-to-rgb (v1 v2 h)
  96   "Compute hue from V1 and V2 H.
  97 Used internally by `color-hsl-to-rgb'."
  98   (cond
  99    ((< h (/ 1.0 6))   (+ v1 (* (- v2 v1) h 6.0)))
 100    ((< h 0.5)         v2)
 101    ((< h (/ 2.0 3))   (+ v1 (* (- v2 v1) (- (/ 2.0 3) h) 6.0)))
 102    (t                 v1)))
 103
 104 (defun color-hsl-to-rgb (H S L)
 105   "Convert hue, saturation and luminance to their RGB representation.
 106 H, S, and L should each be numbers between 0.0 and 1.0, inclusive.
 107 Return a list (RED GREEN BLUE), where each element is between 0.0 and 1.0,
 108 inclusive."
 109   (if (= S 0.0)
 110       (list L L L)
 111     (let* ((m2 (if (<= L 0.5)
 112                    (* L (+ 1.0 S))
 113                  (- (+ L S) (* L S))))
 114            (m1 (- (* 2.0 L) m2)))
 115       (list
 116        (color-hue-to-rgb m1 m2 (mod (+ H (/ 1.0 3)) 1))
 117        (color-hue-to-rgb m1 m2 H)
 118        (color-hue-to-rgb m1 m2 (mod (- H (/ 1.0 3)) 1))))))
 119
 120 (defun color-complement-hex (color)
 121   "Return the color that is the complement of COLOR, in hexadecimal format."
 122   (apply 'color-rgb-to-hex (color-complement color)))
 123
 124 (defun color-rgb-to-hsv (red green blue)
 125   "Convert RGB color components to HSV.
 126 RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
 127 inclusive.  Return a list (HUE SATURATION VALUE), where HUE is
 128 in radians and both SATURATION and VALUE are between 0.0 and 1.0,
 129 inclusive."
 130   (let* ((r (float red))
 131          (g (float green))
 132          (b (float blue))
 133          (max (max r g b))
 134          (min (min r g b)))
 135     (if (< (- max min) 1e-8)
 136         (list 0.0 0.0 0.0)
 137       (list
 138        (/ (* 2 float-pi
 139              (cond ((and (= r g) (= g b)) 0)
 140                    ((and (= r max)
 141                          (>= g b))
 142                     (* 60 (/ (- g b) (- max min))))
 143                    ((and (= r max)
 144                          (< g b))
 145                     (+ 360 (* 60 (/ (- g b) (- max min)))))
 146                    ((= max g)
 147                     (+ 120 (* 60 (/ (- b r) (- max min)))))
 148                    ((= max b)
 149                     (+ 240 (* 60 (/ (- r g) (- max min)))))))
 150           360)
 151        (if (= max 0) 0 (- 1 (/ min max)))
 152        (/ max 255.0)))))
 153
 154 (defun color-rgb-to-hsl (red green blue)
 155   "Convert RGB colors to their HSL representation.
 156 RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
 157 inclusive.  Return a list (HUE SATURATION LUMINANCE), where
 158 each element is between 0.0 and 1.0, inclusive."
 159   (let* ((r red)
 160          (g green)
 161          (b blue)
 162          (max (max r g b))
 163          (min (min r g b))
 164          (delta (- max min))
 165          (l (/ (+ max min) 2.0)))
 166     (if (= delta 0)
 167         (list 0.0 0.0 l)
 168       (let* ((s (if (<= l 0.5) (/ delta (+ max min))
 169                   (/ delta (- 2.0 max min))))
 170              (rc (/ (- max r) delta))
 171              (gc (/ (- max g) delta))
 172              (bc (/ (- max b) delta))
 173              (h  (mod
 174                   (/
 175                    (cond
 176                     ((= r max)      (- bc gc))
 177                     ((= g max)      (+ 2.0 rc (- bc)))
 178                     (t              (+ 4.0 gc (- rc))))
 179                    6.0) 1.0)))
 180         (list h s l)))))
 181
 182 (defun color-srgb-to-xyz (red green blue)
 183   "Convert RED GREEN BLUE colors from the sRGB color space to CIE XYZ.
 184 RED, GREEN and BLUE should be between 0.0 and 1.0, inclusive."
 185   (let ((r (if (<= red 0.04045)
 186                (/ red 12.95)
 187              (expt (/ (+ red 0.055) 1.055) 2.4)))
 188         (g (if (<= green 0.04045)
 189                (/ green 12.95)
 190              (expt (/ (+ green 0.055) 1.055) 2.4)))
 191         (b (if (<= blue 0.04045)
 192                (/ blue 12.95)
 193              (expt (/ (+ blue 0.055) 1.055) 2.4))))
 194     (list (+ (* 0.4124564 r) (* 0.3575761 g) (* 0.1804375 b))
 195           (+ (* 0.21266729 r) (* 0.7151522 g) (* 0.0721750 b))
 196           (+ (* 0.0193339 r) (* 0.1191920 g) (* 0.9503041 b)))))
 197
 198 (defun color-xyz-to-srgb (X Y Z)
 199   "Convert CIE X Y Z colors to sRGB color space."
 200   (let ((r (+ (* 3.2404542 X) (* -1.5371385 Y) (* -0.4985314 Z)))
 201         (g (+ (* -0.9692660 X) (* 1.8760108 Y) (* 0.0415560 Z)))
 202         (b (+ (* 0.0556434 X) (* -0.2040259 Y) (* 1.0572252 Z))))
 203     (list (if (<= r 0.0031308)
 204               (* 12.92 r)
 205             (- (* 1.055 (expt r (/ 1 2.4))) 0.055))
 206           (if (<= g 0.0031308)
 207               (* 12.92 g)
 208             (- (* 1.055 (expt g (/ 1 2.4))) 0.055))
 209           (if (<= b 0.0031308)
 210               (* 12.92 b)
 211             (- (* 1.055 (expt b (/ 1 2.4))) 0.055)))))
 212
 213 (defconst color-d65-xyz '(0.950455 1.0 1.088753)
 214   "D65 white point in CIE XYZ.")
 215
 216 (defconst color-cie-ε (/ 216 24389.0))
 217 (defconst color-cie-κ (/ 24389 27.0))
 218
 219 (defun color-xyz-to-lab (X Y Z &optional white-point)
 220   "Convert CIE XYZ to CIE L*a*b*.
 221 WHITE-POINT specifies the (X Y Z) white point for the
 222 conversion.  If omitted or nil, use `color-d65-xyz'."
 223   (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
 224                (xr (/ X Xr))
 225              (yr (/ Y Yr))
 226              (zr (/ Z Zr))
 227              (fx (if (> xr color-cie-ε)
 228                      (expt xr (/ 1 3.0))
 229                    (/ (+ (* color-cie-κ xr) 16) 116.0)))
 230              (fy (if (> yr color-cie-ε)
 231                      (expt yr (/ 1 3.0))
 232                    (/ (+ (* color-cie-κ yr) 16) 116.0)))
 233              (fz (if (> zr color-cie-ε)
 234                      (expt zr (/ 1 3.0))
 235                    (/ (+ (* color-cie-κ zr) 16) 116.0))))
 236         (list
 237          (- (* 116 fy) 16)                  ; L
 238          (* 500 (- fx fy))                  ; a
 239      (* 200 (- fy fz)))))             ; b
 240
 241 (defun color-lab-to-xyz (L a b &optional white-point)
 242   "Convert CIE L*a*b* to CIE XYZ.
 243 WHITE-POINT specifies the (X Y Z) white point for the
 244 conversion.  If omitted or nil, use `color-d65-xyz'."
 245   (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
 246                (fy (/ (+ L 16) 116.0))
 247              (fz (- fy (/ b 200.0)))
 248              (fx (+ (/ a 500.0) fy))
 249              (xr (if (> (expt fx 3.0) color-cie-ε)
 250                      (expt fx 3.0)
 251                (/ (- (* fx 116) 16) color-cie-κ)))
 252              (yr (if (> L (* color-cie-κ color-cie-ε))
 253                      (expt (/ (+ L 16) 116.0) 3.0)
 254                    (/ L color-cie-κ)))
 255              (zr (if (> (expt fz 3) color-cie-ε)
 256                      (expt fz 3.0)
 257                    (/ (- (* 116 fz) 16) color-cie-κ))))
 258         (list (* xr Xr)                 ; X
 259               (* yr Yr)                 ; Y
 260           (* zr Zr))))                ; Z
 261
 262 (defun color-srgb-to-lab (red green blue)
 263   "Convert RGB to CIE L*a*b*."
 264   (apply 'color-xyz-to-lab (color-srgb-to-xyz red green blue)))
 265
 266 (defun color-lab-to-srgb (L a b)
 267   "Convert CIE L*a*b* to RGB."
 268   (apply 'color-xyz-to-srgb (color-lab-to-xyz L a b)))
 269
 270 (defun color-cie-de2000 (color1 color2 &optional kL kC kH)
 271   "Return the CIEDE2000 color distance between COLOR1 and COLOR2.
 272 Both COLOR1 and COLOR2 should be in CIE L*a*b* format, as
 273 returned by `color-srgb-to-lab' or `color-xyz-to-lab'."
 274   (pcase-let*
 275       ((`(,L₁ ,a₁ ,b₁) color1)
 276        (`(,L₂ ,a₂ ,b₂) color2)
 277        (kL (or kL 1))
 278        (kC (or kC 1))
 279        (kH (or kH 1))
 280        (C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
 281        (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
 282        (C̄ (/ (+ C₁ C₂) 2.0))
 283        (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0)
 284                                (+ (expt C̄ 7.0) (expt 25 7.0)))))))
 285        (a′₁ (* (+ 1 G) a₁))
 286        (a′₂ (* (+ 1 G) a₂))
 287        (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
 288        (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
 289        (h′₁ (if (and (= b₁ 0) (= a′₁ 0))
 290                 0
 291               (let ((v (atan b₁ a′₁)))
 292                 (if (< v 0)
 293                     (+ v (* 2 float-pi))
 294                   v))))
 295        (h′₂ (if (and (= b₂ 0) (= a′₂ 0))
 296                 0
 297               (let ((v (atan b₂ a′₂)))
 298                 (if (< v 0)
 299                     (+ v (* 2 float-pi))
 300                   v))))
 301        (ΔL′ (- L₂ L₁))
 302        (ΔC′ (- C′₂ C′₁))
 303        (Δh′ (cond ((= (* C′₁ C′₂) 0)
 304                    0)
 305                   ((<= (abs (- h′₂ h′₁)) float-pi)
 306                    (- h′₂ h′₁))
 307                   ((> (- h′₂ h′₁) float-pi)
 308                    (- (- h′₂ h′₁) (* 2 float-pi)))
 309                   ((< (- h′₂ h′₁) (- float-pi))
 310                    (+ (- h′₂ h′₁) (* 2 float-pi)))))
 311        (ΔH′ (* 2 (sqrt (* C′₁ C′₂)) (sin (/ Δh′ 2.0))))
 312        (L̄′ (/ (+ L₁ L₂) 2.0))
 313        (C̄′ (/ (+ C′₁ C′₂) 2.0))
 314        (h̄′ (cond ((= (* C′₁ C′₂) 0)
 315                   (+ h′₁ h′₂))
 316                  ((<= (abs (- h′₁ h′₂)) float-pi)
 317                   (/ (+ h′₁ h′₂) 2.0))
 318                  ((< (+ h′₁ h′₂) (* 2 float-pi))
 319                   (/ (+ h′₁ h′₂ (* 2 float-pi)) 2.0))
 320                  ((>= (+ h′₁ h′₂) (* 2 float-pi))
 321                   (/ (+ h′₁ h′₂ (* -2 float-pi)) 2.0))))
 322        (T (+ 1
 323              (- (* 0.17 (cos (- h̄′ (degrees-to-radians 30)))))
 324              (* 0.24 (cos (* h̄′ 2)))
 325              (* 0.32 (cos (+ (* h̄′ 3) (degrees-to-radians 6))))
 326              (- (* 0.20 (cos (- (* h̄′ 4) (degrees-to-radians 63)))))))
 327        (Δθ (* (degrees-to-radians 30)
 328               (exp (- (expt (/ (- h̄′ (degrees-to-radians 275))
 329                                (degrees-to-radians 25)) 2.0)))))
 330        (Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
 331        (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0))
 332                    (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
 333        (Sc (+ 1 (* C̄′ 0.045)))
 334        (Sh (+ 1 (* 0.015 C̄′ T)))
 335        (Rt (- (* (sin (* Δθ 2)) Rc))))
 336         (sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
 337                  (expt (/ ΔC′ (* Sc kC)) 2.0)
 338                  (expt (/ ΔH′ (* Sh kH)) 2.0)
 339                  (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))
 340
 341 (defun color-clamp (value)
 342   "Make sure VALUE is a number between 0.0 and 1.0 inclusive."
 343   (min 1.0 (max 0.0 value)))
 344
 345 (defun color-saturate-hsl (H S L percent)
 346   "Make a color more saturated by a specified amount.
 347 Given a color defined in terms of hue, saturation, and luminance
 348 \(arguments H, S, and L), return a color that is PERCENT more
 349 saturated.  Returns a list (HUE SATURATION LUMINANCE)."
 350   (list H (color-clamp (+ S (/ percent 100.0))) L))
 351
 352 (defun color-saturate-name (name percent)
 353   "Make a color with a specified NAME more saturated by PERCENT.
 354 See `color-saturate-hsl'."
 355   (apply 'color-rgb-to-hex
 356          (apply 'color-hsl-to-rgb
 357                 (apply 'color-saturate-hsl
 358                        (append
 359                         (apply 'color-rgb-to-hsl
 360                                (color-name-to-rgb name))
 361                         (list percent))))))
 362
 363 (defun color-desaturate-hsl (H S L percent)
 364   "Make a color less saturated by a specified amount.
 365 Given a color defined in terms of hue, saturation, and luminance
 366 \(arguments H, S, and L), return a color that is PERCENT less
 367 saturated.  Returns a list (HUE SATURATION LUMINANCE)."
 368   (color-saturate-hsl H S L (- percent)))
 369
 370 (defun color-desaturate-name (name percent)
 371   "Make a color with a specified NAME less saturated by PERCENT.
 372 See `color-desaturate-hsl'."
 373   (color-saturate-name name (- percent)))
 374
 375 (defun color-lighten-hsl (H S L percent)
 376   "Make a color lighter by a specified amount.
 377 Given a color defined in terms of hue, saturation, and luminance
 378 \(arguments H, S, and L), return a color that is PERCENT lighter.
 379 Returns a list (HUE SATURATION LUMINANCE)."
 380   (list H S (color-clamp (+ L (/ percent 100.0)))))
 381
 382 (defun color-lighten-name (name percent)
 383   "Make a color with a specified NAME lighter by PERCENT.
 384 See `color-lighten-hsl'."
 385   (apply 'color-rgb-to-hex
 386          (apply 'color-hsl-to-rgb
 387                 (apply 'color-lighten-hsl
 388                        (append
 389                         (apply 'color-rgb-to-hsl
 390                                (color-name-to-rgb name))
 391                         (list percent))))))
 392
 393 (defun color-darken-hsl (H S L percent)
 394     "Make a color darker by a specified amount.
 395 Given a color defined in terms of hue, saturation, and luminance
 396 \(arguments H, S, and L), return a color that is PERCENT darker.
 397 Returns a list (HUE SATURATION LUMINANCE)."
 398   (color-lighten-hsl H S L (- percent)))
 399
 400 (defun color-darken-name (name percent)
 401   "Make a color with a specified NAME darker by PERCENT.
 402 See `color-darken-hsl'."
 403   (color-lighten-name name (- percent)))
 404
 405 (provide 'color)
 406
 407 ;;; color.el ends here