lisp/gnus/shr-color.el

   1 ;;; shr-color.el --- Simple HTML Renderer color management
   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 handles colors display for shr.
  26
  27 ;;; Code:
  28
  29 (require 'color)
  30
  31 (defgroup shr-color nil
  32   "Simple HTML Renderer colors"
  33   :group 'shr)
  34
  35 (defcustom shr-color-visible-luminance-min 40
  36   "Minimum luminance distance between two colors to be considered visible.
  37 Must be between 0 and 100."
  38   :group 'shr
  39   :type 'float)
  40
  41 (defcustom shr-color-visible-distance-min 5
  42   "Minimum color distance between two colors to be considered visible.
  43 This value is used to compare result for `ciede2000'. Its an
  44 absolute value without any unit."
  45   :group 'shr
  46   :type 'integer)
  47
  48 (defconst shr-color-html-colors-alist
  49   '(("AliceBlue" . "#F0F8FF")
  50     ("AntiqueWhite" . "#FAEBD7")
  51     ("Aqua" . "#00FFFF")
  52     ("Aquamarine" . "#7FFFD4")
  53     ("Azure" . "#F0FFFF")
  54     ("Beige" . "#F5F5DC")
  55     ("Bisque" . "#FFE4C4")
  56     ("Black" . "#000000")
  57     ("BlanchedAlmond" . "#FFEBCD")
  58     ("Blue" . "#0000FF")
  59     ("BlueViolet" . "#8A2BE2")
  60     ("Brown" . "#A52A2A")
  61     ("BurlyWood" . "#DEB887")
  62     ("CadetBlue" . "#5F9EA0")
  63     ("Chartreuse" . "#7FFF00")
  64     ("Chocolate" . "#D2691E")
  65     ("Coral" . "#FF7F50")
  66     ("CornflowerBlue" . "#6495ED")
  67     ("Cornsilk" . "#FFF8DC")
  68     ("Crimson" . "#DC143C")
  69     ("Cyan" . "#00FFFF")
  70     ("DarkBlue" . "#00008B")
  71     ("DarkCyan" . "#008B8B")
  72     ("DarkGoldenRod" . "#B8860B")
  73     ("DarkGray" . "#A9A9A9")
  74     ("DarkGrey" . "#A9A9A9")
  75     ("DarkGreen" . "#006400")
  76     ("DarkKhaki" . "#BDB76B")
  77     ("DarkMagenta" . "#8B008B")
  78     ("DarkOliveGreen" . "#556B2F")
  79     ("Darkorange" . "#FF8C00")
  80     ("DarkOrchid" . "#9932CC")
  81     ("DarkRed" . "#8B0000")
  82     ("DarkSalmon" . "#E9967A")
  83     ("DarkSeaGreen" . "#8FBC8F")
  84     ("DarkSlateBlue" . "#483D8B")
  85     ("DarkSlateGray" . "#2F4F4F")
  86     ("DarkSlateGrey" . "#2F4F4F")
  87     ("DarkTurquoise" . "#00CED1")
  88     ("DarkViolet" . "#9400D3")
  89     ("DeepPink" . "#FF1493")
  90     ("DeepSkyBlue" . "#00BFFF")
  91     ("DimGray" . "#696969")
  92     ("DimGrey" . "#696969")
  93     ("DodgerBlue" . "#1E90FF")
  94     ("FireBrick" . "#B22222")
  95     ("FloralWhite" . "#FFFAF0")
  96     ("ForestGreen" . "#228B22")
  97     ("Fuchsia" . "#FF00FF")
  98     ("Gainsboro" . "#DCDCDC")
  99     ("GhostWhite" . "#F8F8FF")
 100     ("Gold" . "#FFD700")
 101     ("GoldenRod" . "#DAA520")
 102     ("Gray" . "#808080")
 103     ("Grey" . "#808080")
 104     ("Green" . "#008000")
 105     ("GreenYellow" . "#ADFF2F")
 106     ("HoneyDew" . "#F0FFF0")
 107     ("HotPink" . "#FF69B4")
 108     ("IndianRed" . "#CD5C5C")
 109     ("Indigo" . "#4B0082")
 110     ("Ivory" . "#FFFFF0")
 111     ("Khaki" . "#F0E68C")
 112     ("Lavender" . "#E6E6FA")
 113     ("LavenderBlush" . "#FFF0F5")
 114     ("LawnGreen" . "#7CFC00")
 115     ("LemonChiffon" . "#FFFACD")
 116     ("LightBlue" . "#ADD8E6")
 117     ("LightCoral" . "#F08080")
 118     ("LightCyan" . "#E0FFFF")
 119     ("LightGoldenRodYellow" . "#FAFAD2")
 120     ("LightGray" . "#D3D3D3")
 121     ("LightGrey" . "#D3D3D3")
 122     ("LightGreen" . "#90EE90")
 123     ("LightPink" . "#FFB6C1")
 124     ("LightSalmon" . "#FFA07A")
 125     ("LightSeaGreen" . "#20B2AA")
 126     ("LightSkyBlue" . "#87CEFA")
 127     ("LightSlateGray" . "#778899")
 128     ("LightSlateGrey" . "#778899")
 129     ("LightSteelBlue" . "#B0C4DE")
 130     ("LightYellow" . "#FFFFE0")
 131     ("Lime" . "#00FF00")
 132     ("LimeGreen" . "#32CD32")
 133     ("Linen" . "#FAF0E6")
 134     ("Magenta" . "#FF00FF")
 135     ("Maroon" . "#800000")
 136     ("MediumAquaMarine" . "#66CDAA")
 137     ("MediumBlue" . "#0000CD")
 138     ("MediumOrchid" . "#BA55D3")
 139     ("MediumPurple" . "#9370D8")
 140     ("MediumSeaGreen" . "#3CB371")
 141     ("MediumSlateBlue" . "#7B68EE")
 142     ("MediumSpringGreen" . "#00FA9A")
 143     ("MediumTurquoise" . "#48D1CC")
 144     ("MediumVioletRed" . "#C71585")
 145     ("MidnightBlue" . "#191970")
 146     ("MintCream" . "#F5FFFA")
 147     ("MistyRose" . "#FFE4E1")
 148     ("Moccasin" . "#FFE4B5")
 149     ("NavajoWhite" . "#FFDEAD")
 150     ("Navy" . "#000080")
 151     ("OldLace" . "#FDF5E6")
 152     ("Olive" . "#808000")
 153     ("OliveDrab" . "#6B8E23")
 154     ("Orange" . "#FFA500")
 155     ("OrangeRed" . "#FF4500")
 156     ("Orchid" . "#DA70D6")
 157     ("PaleGoldenRod" . "#EEE8AA")
 158     ("PaleGreen" . "#98FB98")
 159     ("PaleTurquoise" . "#AFEEEE")
 160     ("PaleVioletRed" . "#D87093")
 161     ("PapayaWhip" . "#FFEFD5")
 162     ("PeachPuff" . "#FFDAB9")
 163     ("Peru" . "#CD853F")
 164     ("Pink" . "#FFC0CB")
 165     ("Plum" . "#DDA0DD")
 166     ("PowderBlue" . "#B0E0E6")
 167     ("Purple" . "#800080")
 168     ("Red" . "#FF0000")
 169     ("RosyBrown" . "#BC8F8F")
 170     ("RoyalBlue" . "#4169E1")
 171     ("SaddleBrown" . "#8B4513")
 172     ("Salmon" . "#FA8072")
 173     ("SandyBrown" . "#F4A460")
 174     ("SeaGreen" . "#2E8B57")
 175     ("SeaShell" . "#FFF5EE")
 176     ("Sienna" . "#A0522D")
 177     ("Silver" . "#C0C0C0")
 178     ("SkyBlue" . "#87CEEB")
 179     ("SlateBlue" . "#6A5ACD")
 180     ("SlateGray" . "#708090")
 181     ("SlateGrey" . "#708090")
 182     ("Snow" . "#FFFAFA")
 183     ("SpringGreen" . "#00FF7F")
 184     ("SteelBlue" . "#4682B4")
 185     ("Tan" . "#D2B48C")
 186     ("Teal" . "#008080")
 187     ("Thistle" . "#D8BFD8")
 188     ("Tomato" . "#FF6347")
 189     ("Turquoise" . "#40E0D0")
 190     ("Violet" . "#EE82EE")
 191     ("Wheat" . "#F5DEB3")
 192     ("White" . "#FFFFFF")
 193     ("WhiteSmoke" . "#F5F5F5")
 194     ("Yellow" . "#FFFF00")
 195     ("YellowGreen" . "#9ACD32"))
 196   "Alist of HTML colors.
 197 Each entry should have the form (COLOR-NAME . HEXADECIMAL-COLOR).")
 198
 199 (defun shr-color-relative-to-absolute (number)
 200   "Convert a relative NUMBER to absolute. If NUMBER is absolute, return NUMBER.
 201 This will convert \"80 %\" to 204, \"100 %\" to 255 but \"123\" to \"123\"."
 202   (let ((string-length (- (length number) 1)))
 203     ;; Is this a number with %?
 204     (if (eq (elt number string-length) ?%)
 205         (/ (* (string-to-number (substring number 0 string-length)) 255) 100)
 206       (string-to-number number))))
 207
 208 (defun shr-color-hue-to-rgb (x y h)
 209   "Convert X Y H to RGB value."
 210   (when (< h 0) (incf h))
 211   (when (> h 1) (decf h))
 212   (cond ((< h (/ 1 6.0)) (+ x (* (- y x) h 6)))
 213         ((< h 0.5) y)
 214         ((< h (/ 2.0 3.0)) (+ x (* (- y x) (- (/ 2.0 3.0) h) 6)))
 215         (t x)))
 216
 217 (defun shr-color-hsl-to-rgb-fractions (h s l)
 218   "Convert H S L to fractional RGB values."
 219   (let (m1 m2)
 220     (if (<= l 0.5)
 221         (setq m2 (* l (+ s 1)))
 222         (setq m2 (- (+ l s) (* l s))))
 223     (setq m1 (- (* l 2) m2))
 224     (list (shr-color-hue-to-rgb m1 m2 (+ h (/ 1 3.0)))
 225           (shr-color-hue-to-rgb m1 m2 h)
 226           (shr-color-hue-to-rgb m1 m2 (- h (/ 1 3.0))))))
 227
 228 (defun shr-color->hexadecimal (color)
 229   "Convert any color format to hexadecimal representation.
 230 Like rgb() or hsl()."
 231   (when color
 232     (cond
 233      ;; Hexadecimal color: #abc or #aabbcc
 234      ((string-match
 235        "\\(#[0-9a-fA-F]\\{3\\}[0-9a-fA-F]\\{3\\}?\\)"
 236        color)
 237       (match-string 1 color))
 238      ;; rgb() or rgba() colors
 239      ((or (string-match
 240            "rgb(\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*)"
 241            color)
 242           (string-match
 243            "rgba(\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*[0-9]*\.?[0-9]+\s*%?\s*)"
 244            color))
 245       (format "#%02X%02X%02X"
 246               (shr-color-relative-to-absolute (match-string-no-properties 1 color))
 247               (shr-color-relative-to-absolute (match-string-no-properties 2 color))
 248               (shr-color-relative-to-absolute (match-string-no-properties 3 color))))
 249      ;; hsl() or hsla() colors
 250      ((or (string-match
 251            "hsl(\s*\\([0-9]\\{1,3\\}\\)\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*)"
 252            color)
 253           (string-match
 254            "hsla(\s*\\([0-9]\\{1,3\\}\\)\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*[0-9]*\.?[0-9]+\s*%?\s*)"
 255            color))
 256       (let ((h (/ (string-to-number (match-string-no-properties 1 color)) 360.0))
 257             (s (/ (string-to-number (match-string-no-properties 2 color)) 100.0))
 258             (l (/ (string-to-number (match-string-no-properties 3 color)) 100.0)))
 259         (destructuring-bind (r g b)
 260             (shr-color-hsl-to-rgb-fractions h s l)
 261           (color-rgb->hex r g b))))
 262      ;; Color names
 263      ((cdr (assoc-string color shr-color-html-colors-alist t)))
 264      ;; Unrecognized color :(
 265      (t
 266       nil))))
 267
 268 (defun set-minimum-interval (val1 val2 min max interval &optional fixed)
 269   "Set minimum interval between VAL1 and VAL2 to INTERVAL.
 270 The values are bound by MIN and MAX.
 271 If FIXED is t, then val1 will not be touched."
 272   (let ((diff (abs (- val1 val2))))
 273     (unless (>= diff interval)
 274       (if fixed
 275           (let* ((missing (- interval diff))
 276                  ;; If val2 > val1, try to increase val2
 277                  ;; That's the "good direction"
 278                  (val2-good-direction
 279                   (if (> val2 val1)
 280                       (min max (+ val2 missing))
 281                     (max min (- val2 missing))))
 282                  (diff-val2-good-direction-val1 (abs (- val2-good-direction val1))))
 283             (if (>= diff-val2-good-direction-val1 interval)
 284                 (setq val2 val2-good-direction)
 285               ;; Good-direction is not so good, compute bad-direction
 286               (let* ((val2-bad-direction
 287                       (if (> val2 val1)
 288                           (max min (- val1 interval))
 289                         (min max (+ val1 interval))))
 290                      (diff-val2-bad-direction-val1 (abs (- val2-bad-direction val1))))
 291                 (if (>= diff-val2-bad-direction-val1 interval)
 292                     (setq val2 val2-bad-direction)
 293                   ;; Still not good, pick the best and prefer good direction
 294                   (setq val2
 295                         (if (>= diff-val2-good-direction-val1 diff-val2-bad-direction-val1)
 296                             val2-good-direction
 297                           val2-bad-direction))))))
 298         ;; No fixed, move val1 and val2
 299         (let ((missing (/ (- interval diff) 2.0)))
 300           (if (< val1 val2)
 301               (setq val1 (max min (- val1 missing))
 302                     val2 (min max (+ val2 missing)))
 303             (setq val2 (max min (- val2 missing))
 304                   val1 (min max (+ val1 missing))))
 305           (setq diff (abs (- val1 val2)))   ; Recompute diff
 306           (unless (>= diff interval)
 307             ;; Not ok, we hit a boundary
 308             (let ((missing (- interval diff)))
 309               (cond ((= val1 min)
 310                      (setq val2 (+ val2 missing)))
 311                     ((= val2 min)
 312                      (setq val1 (+ val1 missing)))
 313                     ((= val1 max)
 314                      (setq val2 (- val2 missing)))
 315                     ((= val2 max)
 316                      (setq val1 (- val1 missing)))))))))
 317     (list val1 val2)))
 318
 319 (defun shr-color-visible (bg fg &optional fixed-background)
 320   "Check that BG and FG colors are visible if they are drawn on each other.
 321 Return (bg fg) if they are. If they are too similar, two new
 322 colors are returned instead.
 323 If FIXED-BACKGROUND is set, and if the color are not visible, a
 324 new background color will not be computed. Only the foreground
 325 color will be adapted to be visible on BG."
 326   ;; Convert fg and bg to CIE Lab
 327   (let ((fg-norm (color-rgb->normalize fg))
 328         (bg-norm (color-rgb->normalize bg)))
 329     (if (or (null fg-norm)
 330             (null bg-norm))
 331         (list bg fg)
 332       (let* ((fg-lab (apply 'color-rgb->lab fg-norm))
 333              (bg-lab (apply 'color-rgb->lab bg-norm))
 334              ;; Compute color distance using CIE DE 2000
 335              (fg-bg-distance (color-cie-de2000 fg-lab bg-lab))
 336              ;; Compute luminance distance (substract L component)
 337              (luminance-distance (abs (- (car fg-lab) (car bg-lab)))))
 338         (if (and (>= fg-bg-distance shr-color-visible-distance-min)
 339                  (>= luminance-distance shr-color-visible-luminance-min))
 340             (list bg fg)
 341           ;; Not visible, try to change luminance to make them visible
 342           (let ((Ls (set-minimum-interval (car bg-lab) (car fg-lab) 0 100
 343                                           shr-color-visible-luminance-min
 344                                           fixed-background)))
 345             (unless fixed-background
 346               (setcar bg-lab (car Ls)))
 347             (setcar fg-lab (cadr Ls))
 348             (list
 349              (if fixed-background
 350                  bg
 351                (apply 'format "#%02x%02x%02x"
 352                       (mapcar (lambda (x) (* (max (min 1 x) 0) 255))
 353                               (apply 'color-lab->rgb bg-lab))))
 354              (apply 'format "#%02x%02x%02x"
 355                     (mapcar (lambda (x) (* (max (min 1 x) 0) 255))
 356                             (apply 'color-lab->rgb fg-lab))))))))))
 357
 358 (provide 'shr-color)
 359
 360 ;;; shr-color.el ends here