shr.el (shr-tag-color-check): Convert colors to hexadecimal with shr-color->hexadecimal.

shr-color.el (shr-color->hexadecimal): Add converting functions for RGB() or HSL() color representation.
shr.el (shr-tag-font): Add.
 (shr-tag-color-check): New function to get better colors.
 (shr-tag-insert-color-overlay): Factorize code between tag-font and tag-span.
shr-color.el: New file.
color-lab.el: New file.

4 files changed, 460 insertions, 0 deletions

diff --git a/lisp/gnus/ChangeLog b/lisp/gnus/ChangeLog
index 14eaec1052b..d791cf10aaf 100644
--- a/lisp/gnus/ChangeLog
+++ b/lisp/gnus/ChangeLog
@@ -1,5 +1,20 @@
 2010-11-22  Julien Danjou  <julien@danjou.info>
 
+        * shr.el (shr-tag-color-check): Convert colors to hexadecimal with
+        shr-color->hexadecimal.
+
+        * shr-color.el (shr-color->hexadecimal): Add converting functions for
+        RGB() or HSL() color representation.
+
+        * shr.el (shr-tag-font): Add.
+        (shr-tag-color-check): New function to get better colors.
+        (shr-tag-insert-color-overlay): Factorize code between tag-font and
+        tag-span.
+
+        * shr-color.el: New file.
+
+        * color-lab.el: New file.
+
         * gnus-art.el (gnus-url-mailto): Do not downcase args.
 
 2010-11-21  Andrew Cohen  <cohen@andy.bu.edu>
diff --git a/lisp/gnus/color-lab.el b/lisp/gnus/color-lab.el
new file mode 100644
index 00000000000..997bdbfc145
--- /dev/null
+++ b/lisp/gnus/color-lab.el
@@ -0,0 +1,241 @@
+;;; 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)
diff --git a/lisp/gnus/shr-color.el b/lisp/gnus/shr-color.el
new file mode 100644
index 00000000000..127dc68191a
--- /dev/null
+++ b/lisp/gnus/shr-color.el
@@ -0,0 +1,179 @@
+;;; shr-color.el --- Simple HTML Renderer color management
+
+;; 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 handles colors display for shr.
+
+;;; Code:
+
+(require 'color-lab)
+
+(defgroup shr-color nil
+  "Simple HTML Renderer colors"
+  :group 'shr)
+
+(defcustom shr-color-visible-luminance-min 40
+  "Minimum luminance distance between two colors to be considered visible.
+Must be between 0 and 100."
+  :group 'shr
+  :type 'float)
+
+(defcustom shr-color-visible-distance-min 5
+  "Minimum color distance between two colors to be considered visible.
+This value is used to compare result for `ciede2000'. Its an
+absolute value without any unit."
+  :group 'shr
+  :type 'integer)
+
+(defun shr-color-relative-to-absolute (number)
+  "Convert a relative NUMBER to absolute. If NUMBER is absolute, return NUMBER.
+This will convert \"80 %\" to 204, \"100 %\" to 255 but \"123\" to \"123\"."
+  (let ((string-length (- (length number) 1)))
+    ;; Is this a number with %?
+    (if (eq (elt number string-length) ?%)
+        (/ (* (string-to-number (substring number 0 string-length)) 255) 100)
+      (string-to-number number))))
+
+(defun shr-color-hsl-to-rgb-fractions (h s l)
+  "Convert H S L to fractional RGB values."
+  (let (m1 m2)
+    (if (<= l 0.5)
+        (setq m2 (* l (+ s 1)))
+        (setq m2 (- (+ l s) (* l s))))
+    (setq m1 (- (* l 2) m2))
+    (list (rainbow-hue-to-rgb m1 m2 (+ h (/ 1 3.0)))
+          (rainbow-hue-to-rgb m1 m2 h)
+          (rainbow-hue-to-rgb m1 m2 (- h (/ 1 3.0))))))
+
+(defun shr-color->hexadecimal (color)
+  "Convert any color format to hexadecimal representation.
+Like rgb() or hsl()."
+  (when color
+    (cond ((or (string-match
+                "rgb(\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*)"
+                color)
+               (string-match
+                "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*)"
+                color))
+           (format "#%02X%02X%02X"
+                   (shr-color-relative-to-absolute (match-string-no-properties 1 color))
+                   (shr-color-relative-to-absolute (match-string-no-properties 2 color))
+                   (shr-color-relative-to-absolute (match-string-no-properties 3 color))))
+          ((or (string-match
+                "hsl(\s*\\([0-9]\\{1,3\\}\\)\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*)"
+                color)
+               (string-match
+                "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*)"
+                color))
+           (let ((h (/ (string-to-number (match-string-no-properties 1 color)) 360.0))
+                 (s (/ (string-to-number (match-string-no-properties 2 color)) 100.0))
+                 (l (/ (string-to-number (match-string-no-properties 3 color)) 100.0)))
+             (destructuring-bind (r g b)
+                 (rainbow-hsl-to-rgb-fractions h s l)
+               (format "#%02X%02X%02X" (* r 255) (* g 255) (* b 255)))))
+          (t
+           color))))
+
+(defun set-minimum-interval (val1 val2 min max interval &optional fixed)
+  "Set minimum interval between VAL1 and VAL2 to INTERVAL.
+The values are bound by MIN and MAX.
+If FIXED is t, then val1 will not be touched."
+  (let ((diff (abs (- val1 val2))))
+    (unless (>= diff interval)
+      (if fixed
+          (let* ((missing (- interval diff))
+                 ;; If val2 > val1, try to increase val2
+                 ;; That's the "good direction"
+                 (val2-good-direction
+                  (if (> val2 val1)
+                      (min max (+ val2 missing))
+                    (max min (- val2 missing))))
+                 (diff-val2-good-direction-val1 (abs (- val2-good-direction val1))))
+            (if (>= diff-val2-good-direction-val1 interval)
+                (setq val2 val2-good-direction)
+              ;; Good-direction is not so good, compute bad-direction
+              (let* ((val2-bad-direction
+                      (if (> val2 val1)
+                          (max min (- val1 interval))
+                        (min max (+ val1 interval))))
+                     (diff-val2-bad-direction-val1 (abs (- val2-bad-direction val1))))
+                (if (>= diff-val2-bad-direction-val1 interval)
+                    (setq val2 val2-bad-direction)
+                  ;; Still not good, pick the best and prefer good direction
+                  (setq val2
+                        (if (>= diff-val2-good-direction-val1 diff-val2-bad-direction-val1)
+                            val2-good-direction
+                          val2-bad-direction))))))
+        ;; No fixed, move val1 and val2
+        (let ((missing (/ (- interval diff) 2.0)))
+          (if (< val1 val2)
+              (setq val1 (max min (- val1 missing))
+                    val2 (min max (+ val2 missing)))
+            (setq val2 (max min (- val2 missing))
+                  val1 (min max (+ val1 missing))))
+          (setq diff (abs (- val1 val2)))   ; Recompute diff
+          (unless (>= diff interval)
+            ;; Not ok, we hit a boundary
+            (let ((missing (- interval diff)))
+              (cond ((= val1 min)
+                     (setq val2 (+ val2 missing)))
+                    ((= val2 min)
+                     (setq val1 (+ val1 missing)))
+                    ((= val1 max)
+                     (setq val2 (- val2 missing)))
+                    ((= val2 max)
+                     (setq val1 (- val1 missing)))))))))
+    (list val1 val2)))
+
+(defun shr-color-visible (bg fg &optional fixed-background)
+  "Check that BG and FG colors are visible if they are drawn on each other.
+Return t if they are. If they are too similar, two new colors are
+returned instead.
+If FIXED-BACKGROUND is set, and if the color are not visible, a
+new background color will not be computed. Only the foreground
+color will be adapted to be visible on BG."
+  ;; Convert fg and bg to CIE Lab
+  (let* ((fg-lab (apply 'rgb->lab (rgb->normalize fg)))
+         (bg-lab (apply 'rgb->lab (rgb->normalize bg)))
+         ;; Compute color distance using CIE DE 2000
+         (fg-bg-distance (color-lab-ciede2000 fg-lab bg-lab))
+         ;; Compute luminance distance (substract L component)
+         (luminance-distance (abs (- (car fg-lab) (car bg-lab)))))
+    (if (and (>= fg-bg-distance shr-color-visible-distance-min)
+             (>= luminance-distance shr-color-visible-luminance-min))
+        (list bg fg)
+      ;; Not visible, try to change luminance to make them visible
+      (let ((Ls (set-minimum-interval (car bg-lab) (car fg-lab) 0 100
+                                      shr-color-visible-luminance-min
+                                      fixed-background)))
+        (setcar bg-lab (car Ls))
+        (setcar fg-lab (cadr Ls))
+        (list
+         (apply 'format "#%02x%02x%02x"
+                (mapcar (lambda (x) (* (max (min 1 x) 0) 255)) (apply 'lab->rgb bg-lab)))
+         (apply 'format "#%02x%02x%02x"
+                (mapcar (lambda (x) (* (max (min 1 x) 0) 255)) (apply 'lab->rgb fg-lab))))))))
+
+(provide 'shr-color)
+
+;;; shr-color.el ends here
diff --git a/lisp/gnus/shr.el b/lisp/gnus/shr.el
index 6e5800ac1c7..60fa1271939 100644
--- a/lisp/gnus/shr.el
+++ b/lisp/gnus/shr.el
@@ -517,6 +517,31 @@ START, and END."
 (defun shr-tag-s (cont)
   (shr-fontize-cont cont 'strike-through))
 
+(autoload 'shr-color-visible "shr-color")
+(defun shr-tag-color-check (fg &optional bg)
+  "Check that FG is visible on BG."
+  (shr-color-visible (or (shr-color->hexadecimal bg)
+                         (frame-parameter nil 'background-color))
+                     (shr-color->hexadecimal fg) (not bg)))
+
+(defun shr-tag-insert-color-overlay (color start end)
+  (when color
+    (let ((overlay (make-overlay start end)))
+      (overlay-put overlay 'face (cons 'foreground-color
+                                       (cadr (shr-tag-color-check color)))))))
+
+(defun shr-tag-span (cont)
+  (let ((start (point))
+        (color (cdr (assq 'color (shr-parse-style (cdr (assq :style cont)))))))
+    (shr-generic cont)
+    (shr-tag-insert-color-overlay color start (point))))
+
+(defun shr-tag-font (cont)
+  (let ((start (point))
+        (color (cdr (assq :color cont))))
+    (shr-generic cont)
+    (shr-tag-insert-color-overlay color start (point))))
+
 (defun shr-parse-style (style)
   (when style
     (let ((plist nil))