lisp/color.el

   1 ;;; color.el --- Color manipulation library -*- lexical-binding:t -*-
   2
   3 ;; Copyright (C) 2010-2016 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 ;; Emacs < 23.3
  37 (eval-and-compile
  38   (unless (boundp 'float-pi)
  39     (defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))
  40
  41 ;;;###autoload
  42 (defun color-name-to-rgb (color &optional frame)
  43   "Convert COLOR string to a list of normalized RGB components.
  44 COLOR should be a color name (e.g. \"white\") or an RGB triplet
  45 string (e.g. \"#ff12ec\").
  46
  47 Normally the return value is a list of three floating-point
  48 numbers, (RED GREEN BLUE), each between 0.0 and 1.0 inclusive.
  49
  50 Optional argument FRAME specifies the frame where the color is to be
  51 displayed.  If FRAME is omitted or nil, use the selected frame.
  52 If FRAME cannot display COLOR, return nil."
  53   ;; `colors-values' maximum value is either 65535 or 65280 depending on the
  54   ;; display system.  So we use a white conversion to get the max value.
  55   (let ((valmax (float (car (color-values "#ffffff")))))
  56     (mapcar (lambda (x) (/ x valmax)) (color-values color frame))))
  57
  58 (defun color-rgb-to-hex  (red green blue)
  59   "Return hexadecimal notation for the color RED GREEN BLUE.
  60 RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive."
  61   (format "#%02x%02x%02x"
  62           (* red 255) (* green 255) (* blue 255)))
  63
  64 (defun color-complement (color-name)
  65   "Return the color that is the complement of COLOR-NAME.
  66 COLOR-NAME should be a string naming a color (e.g. \"white\"), or
  67 a string specifying a color's RGB components (e.g. \"#ff12ec\")."
  68   (let ((color (color-name-to-rgb color-name)))
  69     (list (- 1.0 (nth 0 color))
  70           (- 1.0 (nth 1 color))
  71           (- 1.0 (nth 2 color)))))
  72
  73 (defun color-gradient (start stop step-number)
  74   "Return a list with STEP-NUMBER colors from START to STOP.
  75 The color list builds a color gradient starting at color START to
  76 color STOP.  It does not include the START and STOP color in the
  77 resulting list."
  78   (let* ((r (nth 0 start))
  79          (g (nth 1 start))
  80          (b (nth 2 start))
  81          (r-step (/ (- (nth 0 stop) r) (1+ step-number)))
  82          (g-step (/ (- (nth 1 stop) g) (1+ step-number)))
  83          (b-step (/ (- (nth 2 stop) b) (1+ step-number)))
  84          result)
  85     (dotimes (_ step-number)
  86       (push (list (setq r (+ r r-step))
  87                   (setq g (+ g g-step))
  88                   (setq b (+ b b-step)))
  89             result))
  90     (nreverse result)))
  91
  92 (defun color-hue-to-rgb (v1 v2 h)
  93   "Compute hue from V1 and V2 H.
  94 Used internally by `color-hsl-to-rgb'."
  95   (cond
  96    ((< h (/ 6.0))     (+ v1 (* (- v2 v1) h 6.0)))
  97    ((< h 0.5)         v2)
  98    ((< h (/ 2.0 3))   (+ v1 (* (- v2 v1) (- (/ 2.0 3) h) 6.0)))
  99    (t                 v1)))
 100
 101 (defun color-hsl-to-rgb (H S L)
 102   "Convert hue, saturation and luminance to their RGB representation.
 103 H, S, and L should each be numbers between 0.0 and 1.0, inclusive.
 104 Return a list (RED GREEN BLUE), where each element is between 0.0 and 1.0,
 105 inclusive."
 106   (if (= S 0.0)
 107       (list L L L)
 108     (let* ((m2 (if (<= L 0.5)
 109                    (* L (+ 1.0 S))
 110                  (- (+ L S) (* L S))))
 111            (m1 (- (* 2.0 L) m2)))
 112       (list
 113        (color-hue-to-rgb m1 m2 (mod (+ H (/ 3.0)) 1))
 114        (color-hue-to-rgb m1 m2 H)
 115        (color-hue-to-rgb m1 m2 (mod (- H (/ 3.0)) 1))))))
 116
 117 (defun color-complement-hex (color)
 118   "Return the color that is the complement of COLOR, in hexadecimal format."
 119   (apply 'color-rgb-to-hex (color-complement color)))
 120
 121 (defun color-rgb-to-hsv (red green blue)
 122   "Convert RGB color components to HSV.
 123 RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
 124 inclusive.  Return a list (HUE SATURATION VALUE), where HUE is
 125 in radians and both SATURATION and VALUE are between 0.0 and 1.0,
 126 inclusive."
 127   (let* ((r (float red))
 128          (g (float green))
 129          (b (float blue))
 130          (max (max r g b))
 131          (min (min r g b)))
 132     (if (< (- max min) 1e-8)
 133         (list 0.0 0.0 min)
 134       (list
 135        (/ (* 2 float-pi
 136              (cond ((and (= r g) (= g b)) 0)
 137                    ((and (= r max)
 138                          (>= g b))
 139                     (* 60 (/ (- g b) (- max min))))
 140                    ((and (= r max)
 141                          (< g b))
 142                     (+ 360 (* 60 (/ (- g b) (- max min)))))
 143                    ((= max g)
 144                     (+ 120 (* 60 (/ (- b r) (- max min)))))
 145                    ((= max b)
 146                     (+ 240 (* 60 (/ (- r g) (- max min)))))))
 147           360)
 148        (if (= max 0) 0 (- 1 (/ min max)))
 149        max))))
 150
 151 (defun color-rgb-to-hsl (red green blue)
 152   "Convert RGB colors to their HSL representation.
 153 RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
 154 inclusive.  Return a list (HUE SATURATION LUMINANCE), where
 155 each element is between 0.0 and 1.0, inclusive."
 156   (let* ((r red)
 157          (g green)
 158          (b blue)
 159          (max (max r g b))
 160          (min (min r g b))
 161          (delta (- max min))
 162          (l (/ (+ max min) 2.0)))
 163     (if (= delta 0)
 164         (list 0.0 0.0 l)
 165       (let* ((s (if (<= l 0.5) (/ delta (+ max min))
 166                   (/ delta (- 2.0 max min))))
 167              (rc (/ (- max r) delta))
 168              (gc (/ (- max g) delta))
 169              (bc (/ (- max b) delta))
 170              (h  (mod
 171                   (/
 172                    (cond
 173                     ((= r max)      (- bc gc))
 174                     ((= g max)      (+ 2.0 rc (- bc)))
 175                     (t              (+ 4.0 gc (- rc))))
 176                    6.0) 1.0)))
 177         (list h s l)))))
 178
 179 (defun color-srgb-to-xyz (red green blue)
 180   "Convert RED GREEN BLUE colors from the sRGB color space to CIE XYZ.
 181 RED, GREEN and BLUE should be between 0.0 and 1.0, inclusive."
 182   (let ((r (if (<= red 0.04045)
 183                (/ red 12.95)
 184              (expt (/ (+ red 0.055) 1.055) 2.4)))
 185         (g (if (<= green 0.04045)
 186                (/ green 12.95)
 187              (expt (/ (+ green 0.055) 1.055) 2.4)))
 188         (b (if (<= blue 0.04045)
 189                (/ blue 12.95)
 190              (expt (/ (+ blue 0.055) 1.055) 2.4))))
 191     (list (+ (* 0.4124564 r) (* 0.3575761 g) (* 0.1804375 b))
 192           (+ (* 0.21266729 r) (* 0.7151522 g) (* 0.0721750 b))
 193           (+ (* 0.0193339 r) (* 0.1191920 g) (* 0.9503041 b)))))
 194
 195 (defun color-xyz-to-srgb (X Y Z)
 196   "Convert CIE X Y Z colors to sRGB color space."
 197   (let ((r (+ (* 3.2404542 X) (* -1.5371385 Y) (* -0.4985314 Z)))
 198         (g (+ (* -0.9692660 X) (* 1.8760108 Y) (* 0.0415560 Z)))
 199         (b (+ (* 0.0556434 X) (* -0.2040259 Y) (* 1.0572252 Z))))
 200     (list (if (<= r 0.0031308)
 201               (* 12.92 r)
 202             (- (* 1.055 (expt r (/ 2.4))) 0.055))
 203           (if (<= g 0.0031308)
 204               (* 12.92 g)
 205             (- (* 1.055 (expt g (/ 2.4))) 0.055))
 206           (if (<= b 0.0031308)
 207               (* 12.92 b)
 208             (- (* 1.055 (expt b (/ 2.4))) 0.055)))))
 209
 210 (defconst color-d65-xyz '(0.950455 1.0 1.088753)
 211   "D65 white point in CIE XYZ.")
 212
 213 (defconst color-cie-ε (/ 216 24389.0))
 214 (defconst color-cie-κ (/ 24389 27.0))
 215
 216 (defun color-xyz-to-lab (X Y Z &optional white-point)
 217   "Convert CIE XYZ to CIE L*a*b*.
 218 WHITE-POINT specifies the (X Y Z) white point for the
 219 conversion.  If omitted or nil, use `color-d65-xyz'."
 220   (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
 221                (xr (/ X Xr))
 222              (yr (/ Y Yr))
 223              (zr (/ Z Zr))
 224              (fx (if (> xr color-cie-ε)
 225                      (expt xr (/ 3.0))
 226                    (/ (+ (* color-cie-κ xr) 16) 116.0)))
 227              (fy (if (> yr color-cie-ε)
 228                      (expt yr (/ 3.0))
 229                    (/ (+ (* color-cie-κ yr) 16) 116.0)))
 230              (fz (if (> zr color-cie-ε)
 231                      (expt zr (/ 3.0))
 232                    (/ (+ (* color-cie-κ zr) 16) 116.0))))
 233         (list
 234          (- (* 116 fy) 16)                  ; L
 235          (* 500 (- fx fy))                  ; a
 236      (* 200 (- fy fz)))))             ; b
 237
 238 (defun color-lab-to-xyz (L a b &optional white-point)
 239   "Convert CIE L*a*b* to CIE XYZ.
 240 WHITE-POINT specifies the (X Y Z) white point for the
 241 conversion.  If omitted or nil, use `color-d65-xyz'."
 242   (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
 243                (fy (/ (+ L 16) 116.0))
 244              (fz (- fy (/ b 200.0)))
 245              (fx (+ (/ a 500.0) fy))
 246              (xr (if (> (expt fx 3.0) color-cie-ε)
 247                      (expt fx 3.0)
 248                (/ (- (* fx 116) 16) color-cie-κ)))
 249              (yr (if (> L (* color-cie-κ color-cie-ε))
 250                      (expt (/ (+ L 16) 116.0) 3.0)
 251                    (/ L color-cie-κ)))
 252              (zr (if (> (expt fz 3) color-cie-ε)
 253                      (expt fz 3.0)
 254                    (/ (- (* 116 fz) 16) color-cie-κ))))
 255         (list (* xr Xr)                 ; X
 256               (* yr Yr)                 ; Y
 257           (* zr Zr))))                ; Z
 258
 259 (defun color-srgb-to-lab (red green blue)
 260   "Convert RGB to CIE L*a*b*."
 261   (apply 'color-xyz-to-lab (color-srgb-to-xyz red green blue)))
 262
 263 (defun color-lab-to-srgb (L a b)
 264   "Convert CIE L*a*b* to RGB."
 265   (apply 'color-xyz-to-srgb (color-lab-to-xyz L a b)))
 266
 267 (defun color-cie-de2000 (color1 color2 &optional kL kC kH)
 268   "Return the CIEDE2000 color distance between COLOR1 and COLOR2.
 269 Both COLOR1 and COLOR2 should be in CIE L*a*b* format, as
 270 returned by `color-srgb-to-lab' or `color-xyz-to-lab'."
 271   (pcase-let*
 272       ((`(,L₁ ,a₁ ,b₁) color1)
 273        (`(,L₂ ,a₂ ,b₂) color2)
 274        (kL (or kL 1))
 275        (kC (or kC 1))
 276        (kH (or kH 1))
 277        (C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
 278        (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
 279        (C̄ (/ (+ C₁ C₂) 2.0))
 280        (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0)
 281                                (+ (expt C̄ 7.0) (expt 25 7.0)))))))
 282        (a′₁ (* (+ 1 G) a₁))
 283        (a′₂ (* (+ 1 G) a₂))
 284        (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
 285        (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
 286        (h′₁ (if (and (= b₁ 0) (= a′₁ 0))
 287                 0
 288               (let ((v (atan b₁ a′₁)))
 289                 (if (< v 0)
 290                     (+ v (* 2 float-pi))
 291                   v))))
 292        (h′₂ (if (and (= b₂ 0) (= a′₂ 0))
 293                 0
 294               (let ((v (atan b₂ a′₂)))
 295                 (if (< v 0)
 296                     (+ v (* 2 float-pi))
 297                   v))))
 298        (ΔL′ (- L₂ L₁))
 299        (ΔC′ (- C′₂ C′₁))
 300        (Δh′ (cond ((= (* C′₁ C′₂) 0)
 301                    0)
 302                   ((<= (abs (- h′₂ h′₁)) float-pi)
 303                    (- h′₂ h′₁))
 304                   ((> (- h′₂ h′₁) float-pi)
 305                    (- (- h′₂ h′₁) (* 2 float-pi)))
 306                   ((< (- h′₂ h′₁) (- float-pi))
 307                    (+ (- h′₂ h′₁) (* 2 float-pi)))))
 308        (ΔH′ (* 2 (sqrt (* C′₁ C′₂)) (sin (/ Δh′ 2.0))))
 309        (L̄′ (/ (+ L₁ L₂) 2.0))
 310        (C̄′ (/ (+ C′₁ C′₂) 2.0))
 311        (h̄′ (cond ((= (* C′₁ C′₂) 0)
 312                   (+ h′₁ h′₂))
 313                  ((<= (abs (- h′₁ h′₂)) float-pi)
 314                   (/ (+ h′₁ h′₂) 2.0))
 315                  ((< (+ h′₁ h′₂) (* 2 float-pi))
 316                   (/ (+ h′₁ h′₂ (* 2 float-pi)) 2.0))
 317                  ((>= (+ h′₁ h′₂) (* 2 float-pi))
 318                   (/ (+ h′₁ h′₂ (* -2 float-pi)) 2.0))))
 319        (T (+ 1
 320              (- (* 0.17 (cos (- h̄′ (degrees-to-radians 30)))))
 321              (* 0.24 (cos (* h̄′ 2)))
 322              (* 0.32 (cos (+ (* h̄′ 3) (degrees-to-radians 6))))
 323              (- (* 0.20 (cos (- (* h̄′ 4) (degrees-to-radians 63)))))))
 324        (Δθ (* (degrees-to-radians 30)
 325               (exp (- (expt (/ (- h̄′ (degrees-to-radians 275))
 326                                (degrees-to-radians 25)) 2.0)))))
 327        (Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
 328        (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0))
 329                    (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
 330        (Sc (+ 1 (* C̄′ 0.045)))
 331        (Sh (+ 1 (* 0.015 C̄′ T)))
 332        (Rt (- (* (sin (* Δθ 2)) Rc))))
 333         (sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
 334                  (expt (/ ΔC′ (* Sc kC)) 2.0)
 335                  (expt (/ ΔH′ (* Sh kH)) 2.0)
 336                  (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))
 337
 338 (defun color-clamp (value)
 339   "Make sure VALUE is a number between 0.0 and 1.0 inclusive."
 340   (min 1.0 (max 0.0 value)))
 341
 342 (defun color-saturate-hsl (H S L percent)
 343   "Make a color more saturated by a specified amount.
 344 Given a color defined in terms of hue, saturation, and luminance
 345 \(arguments H, S, and L), return a color that is PERCENT more
 346 saturated.  Returns a list (HUE SATURATION LUMINANCE)."
 347   (list H (color-clamp (+ S (/ percent 100.0))) L))
 348
 349 (defun color-saturate-name (name percent)
 350   "Make a color with a specified NAME more saturated by PERCENT.
 351 See `color-saturate-hsl'."
 352   (apply 'color-rgb-to-hex
 353          (apply 'color-hsl-to-rgb
 354                 (apply 'color-saturate-hsl
 355                        (append
 356                         (apply 'color-rgb-to-hsl
 357                                (color-name-to-rgb name))
 358                         (list percent))))))
 359
 360 (defun color-desaturate-hsl (H S L percent)
 361   "Make a color less saturated by a specified amount.
 362 Given a color defined in terms of hue, saturation, and luminance
 363 \(arguments H, S, and L), return a color that is PERCENT less
 364 saturated.  Returns a list (HUE SATURATION LUMINANCE)."
 365   (color-saturate-hsl H S L (- percent)))
 366
 367 (defun color-desaturate-name (name percent)
 368   "Make a color with a specified NAME less saturated by PERCENT.
 369 See `color-desaturate-hsl'."
 370   (color-saturate-name name (- percent)))
 371
 372 (defun color-lighten-hsl (H S L percent)
 373   "Make a color lighter by a specified amount.
 374 Given a color defined in terms of hue, saturation, and luminance
 375 \(arguments H, S, and L), return a color that is PERCENT lighter.
 376 Returns a list (HUE SATURATION LUMINANCE)."
 377   (list H S (color-clamp (+ L (/ percent 100.0)))))
 378
 379 (defun color-lighten-name (name percent)
 380   "Make a color with a specified NAME lighter by PERCENT.
 381 See `color-lighten-hsl'."
 382   (apply 'color-rgb-to-hex
 383          (apply 'color-hsl-to-rgb
 384                 (apply 'color-lighten-hsl
 385                        (append
 386                         (apply 'color-rgb-to-hsl
 387                                (color-name-to-rgb name))
 388                         (list percent))))))
 389
 390 (defun color-darken-hsl (H S L percent)
 391     "Make a color darker by a specified amount.
 392 Given a color defined in terms of hue, saturation, and luminance
 393 \(arguments H, S, and L), return a color that is PERCENT darker.
 394 Returns a list (HUE SATURATION LUMINANCE)."
 395   (color-lighten-hsl H S L (- percent)))
 396
 397 (defun color-darken-name (name percent)
 398   "Make a color with a specified NAME darker by PERCENT.
 399 See `color-darken-hsl'."
 400   (color-lighten-name name (- percent)))
 401
 402 (provide 'color)
 403
 404 ;;; color.el ends here