Adds DIN99o color difference; v 0.1.3

CHANGELOG.md

@@ -0,0 +1,3 @@
+### 0.1.3
+
+Addeed the DIN99o Delta-E color difference formula.

README.md

@@ -1,6 +1,6 @@
 # d3-color-difference
 
-See this [Observable notebook](https://beta.observablehq.com/@danburzo/color-difference-formulas-with-d3-color-difference).
+See this [Observable notebook](https://beta.observablehq.com/@danburzo/color-difference-formulas-with-d3-color-difference) for a demonstration.
 
 ## Installing
 
@@ -64,6 +64,14 @@ _Note:_ ΔE\*<sub>CMC</sub> is not considered a metric since it's not symmetrica
 
 Returns a [CMC l:c (1984)][CMC] difference function with custom weighting parameters.
 
+<a name="differenceDin99o" href="#differenceDin99o">#</a> d3.__differenceDin99o__(_a_, _b_) [<>](https://github.com/danburzo/d3-color-difference/blob/master/src/din99o.js "Source")
+
+Computes the [DIN99o][DIN99oDE] ΔE\*<sub>99o</sub> color difference between the colors _a_ and _b_. The computation is done in the [DIN99o][DIN99o] color space with the default weights _kCH = kE = 1_.
+
+<a name="differenceDin99oWeighted" href="#differenceDin99oWeighted">#</a> d3.__differenceDin99oWeighted__(_kCH_, _kE_) [<>](https://github.com/danburzo/d3-color-difference/blob/master/src/din99o.js "Source")
+
+Returns a [DIN99o][DIN99oDE] difference function with custom weighting parameters.
+
 ### Opacity
 
 <a name="differenceWithOpacity" href="#differenceWithOpacity">#</a> d3.__differenceWithOpacity__(_differenceFunction_, _a_, _b_) [<>](https://github.com/danburzo/d3-color-difference/blob/master/src/withOpacity.js "Source")
@@ -76,6 +84,8 @@ The difference functions don't take the colors' alpha channel into account when
 [CIE94]: https://en.wikipedia.org/wiki/Color_difference#CIE94
 [CIEDE2000]: https://en.wikipedia.org/wiki/Color_difference#CIEDE2000
 [CMC]: https://en.wikipedia.org/wiki/Color_difference#CMC_l:c_(1984)
+[DIN99o]: https://de.wikipedia.org/wiki/DIN99-Farbraum
+[DIN99oDE]: https://de.wikipedia.org/wiki/DIN99-Farbraum#Farbabstandsformel
 [RGB]: https://github.com/d3/d3-color#rgb
 [HSL]: https://github.com/d3/d3-color#hsl
 [Lab]: https://github.com/d3/d3-color#lab

index.js

@@ -8,4 +8,5 @@ export {
 } from './src/euclidean';
 export { default as differenceCie94, differenceCie94Weighted } from './src/cie94';
 export { default as differenceCiede2000, differenceCiede2000Weighted } from './src/ciede2000';
-export { default as differenceCmc, differenceCmcWeighted } from './src/cmc';
+export { default as differenceCmc, differenceCmcWeighted } from './src/cmc';
+export { default as differenceDin99o, differenceDin99oWeighted } from './src/din99o.js';

package.json

@@ -1,6 +1,6 @@
 {
   "name": "d3-color-difference",
-  "version": "0.1.1",
+  "version": "0.1.3",
   "main": "build/d3-color-difference.js",
   "module": "index",
   "jsnext:main": "index",
@@ -11,6 +11,16 @@
       "name": "Dan Burzo",
       "url": "http://danburzo.ro"
   },
+  "keywords": [
+    "d3",
+    "d3-color",
+    "color",
+    "color-difference",
+    "cie76",
+    "cie94",
+    "ciede2000",
+    "cmc"
+  ],
   "devDependencies": {
     "eslint": "^4.19.1",
     "package-preamble": "^0.1.0",

src/din99o.js

@@ -0,0 +1,39 @@
+import { lab } from 'd3-color';
+import { euclidean } from './euclidean';
+
+var θ = 26 / 180 * Math.PI;
+var cosθ = Math.cos(θ);
+var sinθ = Math.sin(θ);
+var factor = 100/Math.log(139/100); // ~ 303.67
+
+function din99o(color, kCH, kE) {
+	var l = factor / kE * Math.log(1 + 0.0039 * color.l);
+	if (color.a === 0 && color.b === 0) {
+		return lab(l, 0, 0); // achromatic colors
+	}
+	var e = color.a * cosθ + color.b * sinθ;
+	var f = 0.83 * (color.b * cosθ - color.a * sinθ);
+	var G = Math.sqrt(e * e + f * f);
+	var c = Math.log(1 + 0.075 * G) / (0.0435 * kCH * kE);
+	var h = (Math.atan2(f, e) + θ) / Math.PI * 180;
+	return lab(l, c * Math.cos(h / 180 * Math.PI), c * Math.sin(h / 180 * Math.PI));
+}
+
+function differenceDin99o(kCH, kE) {
+
+	kCH = kCH !== undefined ? kCH : 1;
+	kE = kE !== undefined ? kE : 1;
+
+	return function(std, smp) {
+		std = din99o(lab(std), kCH, kE);
+		smp = din99o(lab(smp), kCH, kE);
+		return euclidean(std.l, std.a, std.b, smp.l, smp.a, smp.b);
+	}
+}
+
+var differenceDin99oDefault = differenceDin99o();
+
+export {
+	differenceDin99oDefault as default,
+	differenceDin99o as differenceDin99oWeighted
+}

src/euclidean.js

@@ -30,6 +30,7 @@ function differenceEuclideanCubehelix(std, smp) {
 }
 
 export {
+	euclidean,
 	differenceEuclideanRGB,
 	differenceEuclideanLab,
 	differenceEuclideanHcl,

test/din99o-test.js

@@ -0,0 +1,9 @@
+var tape = require('tape');
+var diff = require('../');
+
+tape('', function(test) {
+
+	test.equal(diff.differenceDin99o('red', 'green'), 68.61703579396708);
+
+	test.end();
+});