-;;; color.el --- Color manipulation laboratory routines -*- coding: utf-8; -*-
+;;; color.el --- Color manipulation library -*- lexical-binding:t -*-
-;; Copyright (C) 2010, 2011 Free Software Foundation, Inc.
+;; Copyright (C) 2010-2016 Free Software Foundation, Inc.
-;; Author: Julien Danjou <julien@danjou.info>
-;; Keywords: html
+;; Authors: Julien Danjou <julien@danjou.info>
+;; Drew Adams <drew.adams@oracle.com>
+;; Keywords: lisp, faces, color, hex, rgb, hsv, hsl, cie-lab, background
;; This file is part of GNU Emacs.
;;; Commentary:
-;; This package provides color manipulation functions.
+;; This package provides functions for manipulating colors, including
+;; converting between color representations, computing color
+;; complements, and computing CIEDE2000 color distances.
+;;
+;; Supported color representations include RGB (red, green, blue), HSV
+;; (hue, saturation, value), HSL (hue, saturation, luminance), sRGB,
+;; CIE XYZ, and CIE L*a*b* color components.
;;; Code:
-(eval-when-compile
- (require 'cl))
-
;; Emacs < 23.3
(eval-and-compile
(unless (boundp 'float-pi)
(defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")))
-(defun color-rgb->hex (red green blue)
- "Return hexadecimal notation for RED GREEN BLUE color.
-RED GREEN BLUE must be values between 0 and 1 inclusively."
+;;;###autoload
+(defun color-name-to-rgb (color &optional frame)
+ "Convert COLOR string to a list of normalized RGB components.
+COLOR should be a color name (e.g. \"white\") or an RGB triplet
+string (e.g. \"#ff12ec\").
+
+Normally the return value is a list of three floating-point
+numbers, (RED GREEN BLUE), each between 0.0 and 1.0 inclusive.
+
+Optional argument FRAME specifies the frame where the color is to be
+displayed. If FRAME is omitted or nil, use the selected frame.
+If FRAME cannot display COLOR, return nil."
+ ;; `colors-values' maximum value is either 65535 or 65280 depending on the
+ ;; display system. So we use a white conversion to get the max value.
+ (let ((valmax (float (car (color-values "#ffffff")))))
+ (mapcar (lambda (x) (/ x valmax)) (color-values color frame))))
+
+(defun color-rgb-to-hex (red green blue)
+ "Return hexadecimal notation for the color RED GREEN BLUE.
+RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive."
(format "#%02x%02x%02x"
(* red 255) (* green 255) (* blue 255)))
-(defun color-complement (color)
- "Return the color that is the complement of COLOR."
- (let ((color (color-rgb->normalize color)))
- (list (- 1.0 (car color))
- (- 1.0 (cadr color))
- (- 1.0 (caddr color)))))
+(defun color-complement (color-name)
+ "Return the color that is the complement of COLOR-NAME.
+COLOR-NAME should be a string naming a color (e.g. \"white\"), or
+a string specifying a color's RGB components (e.g. \"#ff12ec\")."
+ (let ((color (color-name-to-rgb color-name)))
+ (list (- 1.0 (nth 0 color))
+ (- 1.0 (nth 1 color))
+ (- 1.0 (nth 2 color)))))
+
+(defun color-gradient (start stop step-number)
+ "Return a list with STEP-NUMBER colors from START to STOP.
+The color list builds a color gradient starting at color START to
+color STOP. It does not include the START and STOP color in the
+resulting list."
+ (let* ((r (nth 0 start))
+ (g (nth 1 start))
+ (b (nth 2 start))
+ (r-step (/ (- (nth 0 stop) r) (1+ step-number)))
+ (g-step (/ (- (nth 1 stop) g) (1+ step-number)))
+ (b-step (/ (- (nth 2 stop) b) (1+ step-number)))
+ result)
+ (dotimes (_ step-number)
+ (push (list (setq r (+ r r-step))
+ (setq g (+ g g-step))
+ (setq b (+ b b-step)))
+ result))
+ (nreverse result)))
+
+(defun color-hue-to-rgb (v1 v2 h)
+ "Compute hue from V1 and V2 H.
+Used internally by `color-hsl-to-rgb'."
+ (cond
+ ((< h (/ 6.0)) (+ v1 (* (- v2 v1) h 6.0)))
+ ((< h 0.5) v2)
+ ((< h (/ 2.0 3)) (+ v1 (* (- v2 v1) (- (/ 2.0 3) h) 6.0)))
+ (t v1)))
+
+(defun color-hsl-to-rgb (H S L)
+ "Convert hue, saturation and luminance to their RGB representation.
+H, S, and L should each be numbers between 0.0 and 1.0, inclusive.
+Return a list (RED GREEN BLUE), where each element is between 0.0 and 1.0,
+inclusive."
+ (if (= S 0.0)
+ (list L L L)
+ (let* ((m2 (if (<= L 0.5)
+ (* L (+ 1.0 S))
+ (- (+ L S) (* L S))))
+ (m1 (- (* 2.0 L) m2)))
+ (list
+ (color-hue-to-rgb m1 m2 (mod (+ H (/ 3.0)) 1))
+ (color-hue-to-rgb m1 m2 H)
+ (color-hue-to-rgb m1 m2 (mod (- H (/ 3.0)) 1))))))
(defun color-complement-hex (color)
"Return the color that is the complement of COLOR, in hexadecimal format."
- (apply 'color-rgb->hex (color-complement color)))
+ (apply 'color-rgb-to-hex (color-complement color)))
-(defun color-rgb->hsv (red green blue)
- "Convert RED GREEN BLUE values to HSV representation.
-Hue is in radians. Saturation and values are between 0 and 1
-inclusively."
- (let* ((r (float red))
+(defun color-rgb-to-hsv (red green blue)
+ "Convert RGB color components to HSV.
+RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
+inclusive. Return a list (HUE SATURATION VALUE), where HUE is
+in radians and both SATURATION and VALUE are between 0.0 and 1.0,
+inclusive."
+ (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 color-rgb->hsl (red green blue)
- "Convert RED GREEN BLUE colors to their HSL representation.
-RED, GREEN and BLUE must be between 0 and 1 inclusively."
+ (if (< (- max min) 1e-8)
+ (list 0.0 0.0 min)
+ (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))))
+
+(defun color-rgb-to-hsl (red green blue)
+ "Convert RGB colors to their HSL representation.
+RED, GREEN, and BLUE should each be numbers between 0.0 and 1.0,
+inclusive. Return a list (HUE SATURATION LUMINANCE), where
+each element is between 0.0 and 1.0, inclusive."
(let* ((r red)
(g green)
(b blue)
(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 color-srgb->xyz (red green blue)
- "Converts RED GREEN BLUE colors from the sRGB color space to CIE XYZ.
-RED, BLUE and GREEN must be between 0 and 1 inclusively."
+ (if (= delta 0)
+ (list 0.0 0.0 l)
+ (let* ((s (if (<= l 0.5) (/ delta (+ max min))
+ (/ delta (- 2.0 max min))))
+ (rc (/ (- max r) delta))
+ (gc (/ (- max g) delta))
+ (bc (/ (- max b) delta))
+ (h (mod
+ (/
+ (cond
+ ((= r max) (- bc gc))
+ ((= g max) (+ 2.0 rc (- bc)))
+ (t (+ 4.0 gc (- rc))))
+ 6.0) 1.0)))
+ (list h s l)))))
+
+(defun color-srgb-to-xyz (red green blue)
+ "Convert RED GREEN BLUE colors from the sRGB color space to CIE XYZ.
+RED, GREEN and BLUE should be between 0.0 and 1.0, inclusive."
(let ((r (if (<= red 0.04045)
(/ red 12.95)
(expt (/ (+ red 0.055) 1.055) 2.4)))
(+ (* 0.21266729 r) (* 0.7151522 g) (* 0.0721750 b))
(+ (* 0.0193339 r) (* 0.1191920 g) (* 0.9503041 b)))))
-(defun color-xyz->srgb (X Y Z)
- "Converts CIE X Y Z colors to sRGB color space."
+(defun color-xyz-to-srgb (X Y Z)
+ "Convert CIE X Y Z colors to sRGB color space."
(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))
+ (- (* 1.055 (expt r (/ 2.4))) 0.055))
(if (<= g 0.0031308)
(* 12.92 g)
- (- (* 1.055 (expt g (/ 1 2.4))) 0.055))
+ (- (* 1.055 (expt g (/ 2.4))) 0.055))
(if (<= b 0.0031308)
(* 12.92 b)
- (- (* 1.055 (expt b (/ 1 2.4))) 0.055)))))
+ (- (* 1.055 (expt b (/ 2.4))) 0.055)))))
(defconst color-d65-xyz '(0.950455 1.0 1.088753)
"D65 white point in CIE XYZ.")
(defconst color-cie-ε (/ 216 24389.0))
(defconst color-cie-κ (/ 24389 27.0))
-(defun color-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-d65-xyz' is used."
- (destructuring-bind (Xr Yr Zr) (or white-point color-d65-xyz)
- (let* ((xr (/ X Xr))
+(defun color-xyz-to-lab (X Y Z &optional white-point)
+ "Convert CIE XYZ to CIE L*a*b*.
+WHITE-POINT specifies the (X Y Z) white point for the
+conversion. If omitted or nil, use `color-d65-xyz'."
+ (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
+ (xr (/ X Xr))
(yr (/ Y Yr))
(zr (/ Z Zr))
(fx (if (> xr color-cie-ε)
- (expt xr (/ 1 3.0))
+ (expt xr (/ 3.0))
(/ (+ (* color-cie-κ xr) 16) 116.0)))
(fy (if (> yr color-cie-ε)
- (expt yr (/ 1 3.0))
+ (expt yr (/ 3.0))
(/ (+ (* color-cie-κ yr) 16) 116.0)))
(fz (if (> zr color-cie-ε)
- (expt zr (/ 1 3.0))
+ (expt zr (/ 3.0))
(/ (+ (* color-cie-κ zr) 16) 116.0))))
(list
(- (* 116 fy) 16) ; L
(* 500 (- fx fy)) ; a
- (* 200 (- fy fz)))))) ; b
-
-(defun color-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-d65-xyz' is used."
- (destructuring-bind (Xr Yr Zr) (or white-point color-d65-xyz)
- (let* ((fy (/ (+ L 16) 116.0))
+ (* 200 (- fy fz))))) ; b
+
+(defun color-lab-to-xyz (L a b &optional white-point)
+ "Convert CIE L*a*b* to CIE XYZ.
+WHITE-POINT specifies the (X Y Z) white point for the
+conversion. If omitted or nil, use `color-d65-xyz'."
+ (pcase-let* ((`(,Xr ,Yr ,Zr) (or white-point color-d65-xyz))
+ (fy (/ (+ L 16) 116.0))
(fz (- fy (/ b 200.0)))
(fx (+ (/ a 500.0) fy))
(xr (if (> (expt fx 3.0) color-cie-ε)
(/ (- (* 116 fz) 16) color-cie-κ))))
(list (* xr Xr) ; X
(* yr Yr) ; Y
- (* zr Zr))))) ; Z
+ (* zr Zr)))) ; Z
-(defun color-srgb->lab (red green blue)
- "Converts RGB to CIE L*a*b*."
- (apply 'color-xyz->lab (color-srgb->xyz red green blue)))
+(defun color-srgb-to-lab (red green blue)
+ "Convert RGB to CIE L*a*b*."
+ (apply 'color-xyz-to-lab (color-srgb-to-xyz red green blue)))
-(defun color-rgb->normalize (color)
- "Normalize a RGB color to values between 0 and 1 inclusively."
- (mapcar (lambda (x) (/ x 65535.0)) (x-color-values color)))
-
-(defun color-lab->srgb (L a b)
- "Converts CIE L*a*b* to RGB."
- (apply 'color-xyz->srgb (color-lab->xyz L a b)))
+(defun color-lab-to-srgb (L a b)
+ "Convert CIE L*a*b* to RGB."
+ (apply 'color-xyz-to-srgb (color-lab-to-xyz L a b)))
(defun color-cie-de2000 (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 2.0) (expt b₁ 2.0))))
- (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
- (C̄ (/ (+ C₁ C₂) 2.0))
- (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0) (+ (expt C̄ 7.0) (expt 25 7.0)))))))
- (a′₁ (* (+ 1 G) a₁))
- (a′₂ (* (+ 1 G) a₂))
- (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
- (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
- (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)) 2.0)))))
- (Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
- (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0)) (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
- (Sc (+ 1 (* C̄′ 0.045)))
- (Sh (+ 1 (* 0.015 C̄′ T)))
- (Rt (- (* (sin (* Δθ 2)) Rc))))
+ "Return the CIEDE2000 color distance between COLOR1 and COLOR2.
+Both COLOR1 and COLOR2 should be in CIE L*a*b* format, as
+returned by `color-srgb-to-lab' or `color-xyz-to-lab'."
+ (pcase-let*
+ ((`(,L₁ ,a₁ ,b₁) color1)
+ (`(,L₂ ,a₂ ,b₂) color2)
+ (kL (or kL 1))
+ (kC (or kC 1))
+ (kH (or kH 1))
+ (C₁ (sqrt (+ (expt a₁ 2.0) (expt b₁ 2.0))))
+ (C₂ (sqrt (+ (expt a₂ 2.0) (expt b₂ 2.0))))
+ (C̄ (/ (+ C₁ C₂) 2.0))
+ (G (* 0.5 (- 1 (sqrt (/ (expt C̄ 7.0)
+ (+ (expt C̄ 7.0) (expt 25 7.0)))))))
+ (a′₁ (* (+ 1 G) a₁))
+ (a′₂ (* (+ 1 G) a₂))
+ (C′₁ (sqrt (+ (expt a′₁ 2.0) (expt b₁ 2.0))))
+ (C′₂ (sqrt (+ (expt a′₂ 2.0) (expt b₂ 2.0))))
+ (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)) 2.0)))))
+ (Rc (* 2 (sqrt (/ (expt C̄′ 7.0) (+ (expt C̄′ 7.0) (expt 25.0 7.0))))))
+ (Sl (+ 1 (/ (* 0.015 (expt (- L̄′ 50) 2.0))
+ (sqrt (+ 20 (expt (- L̄′ 50) 2.0))))))
+ (Sc (+ 1 (* C̄′ 0.045)))
+ (Sh (+ 1 (* 0.015 C̄′ T)))
+ (Rt (- (* (sin (* Δθ 2)) Rc))))
(sqrt (+ (expt (/ ΔL′ (* Sl kL)) 2.0)
(expt (/ ΔC′ (* Sc kC)) 2.0)
(expt (/ ΔH′ (* Sh kH)) 2.0)
- (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))))
+ (* Rt (/ ΔC′ (* Sc kC)) (/ ΔH′ (* Sh kH)))))))
+
+(defun color-clamp (value)
+ "Make sure VALUE is a number between 0.0 and 1.0 inclusive."
+ (min 1.0 (max 0.0 value)))
+
+(defun color-saturate-hsl (H S L percent)
+ "Make a color more saturated by a specified amount.
+Given a color defined in terms of hue, saturation, and luminance
+\(arguments H, S, and L), return a color that is PERCENT more
+saturated. Returns a list (HUE SATURATION LUMINANCE)."
+ (list H (color-clamp (+ S (/ percent 100.0))) L))
+
+(defun color-saturate-name (name percent)
+ "Make a color with a specified NAME more saturated by PERCENT.
+See `color-saturate-hsl'."
+ (apply 'color-rgb-to-hex
+ (apply 'color-hsl-to-rgb
+ (apply 'color-saturate-hsl
+ (append
+ (apply 'color-rgb-to-hsl
+ (color-name-to-rgb name))
+ (list percent))))))
+
+(defun color-desaturate-hsl (H S L percent)
+ "Make a color less saturated by a specified amount.
+Given a color defined in terms of hue, saturation, and luminance
+\(arguments H, S, and L), return a color that is PERCENT less
+saturated. Returns a list (HUE SATURATION LUMINANCE)."
+ (color-saturate-hsl H S L (- percent)))
+
+(defun color-desaturate-name (name percent)
+ "Make a color with a specified NAME less saturated by PERCENT.
+See `color-desaturate-hsl'."
+ (color-saturate-name name (- percent)))
+
+(defun color-lighten-hsl (H S L percent)
+ "Make a color lighter by a specified amount.
+Given a color defined in terms of hue, saturation, and luminance
+\(arguments H, S, and L), return a color that is PERCENT lighter.
+Returns a list (HUE SATURATION LUMINANCE)."
+ (list H S (color-clamp (+ L (/ percent 100.0)))))
+
+(defun color-lighten-name (name percent)
+ "Make a color with a specified NAME lighter by PERCENT.
+See `color-lighten-hsl'."
+ (apply 'color-rgb-to-hex
+ (apply 'color-hsl-to-rgb
+ (apply 'color-lighten-hsl
+ (append
+ (apply 'color-rgb-to-hsl
+ (color-name-to-rgb name))
+ (list percent))))))
+
+(defun color-darken-hsl (H S L percent)
+ "Make a color darker by a specified amount.
+Given a color defined in terms of hue, saturation, and luminance
+\(arguments H, S, and L), return a color that is PERCENT darker.
+Returns a list (HUE SATURATION LUMINANCE)."
+ (color-lighten-hsl H S L (- percent)))
+
+(defun color-darken-name (name percent)
+ "Make a color with a specified NAME darker by PERCENT.
+See `color-darken-hsl'."
+ (color-lighten-name name (- percent)))
(provide 'color)