diff --git a/README.md b/README.md
index 80d7808..69761a2 100644
--- a/README.md
+++ b/README.md
@@ -712,18 +712,17 @@ colord("#e60000").isReadable("#ffff47", { level: "AAA", size: "large" }); // tru
- .delta(color2 = "#FFF", options?) (lab plugin)
+ .delta(color2 = "#FFF") (lab plugin)
Calculates the perceived color difference between two colors.
The difference calculated according to [Delta E2000](https://en.wikipedia.org/wiki/Color_difference#CIEDE2000).
-
-Returns the normalized value in range from [0, 1], where 0 is the same color and 1 are completely different.
+The return value is `0` if the colors are equal, `1` if they are entirely different.
```js
-colord("#3296fa").delta("#197dc8") // 0.099
-colord("#faf0c8").delta("#fff") // 0.148
-colord("#afafaf").delta("#b4b4b4") // 0.014
-colord("#000").delta("#fff") // 1.0
+colord("#3296fa").delta("#197dc8"); // 0.099
+colord("#faf0c8").delta("#ffffff"); // 0.148
+colord("#afafaf").delta("#b4b4b4"); // 0.014
+colord("#000000").delta("#ffffff"); // 1
```
@@ -842,11 +841,11 @@ colord("hwb(210 0% 60% / 50%)").toHex(); // "#00336680"
- lab (CIE LAB color space) 1.5 KB
+ lab (CIE LAB color space) 1.4 KB
Adds support of [CIE LAB](https://en.wikipedia.org/wiki/CIELAB_color_space) color model. The conversion logic is ported from [CSS Color Module Level 4 Specification](https://www.w3.org/TR/css-color-4/#color-conversion-code).
-Also plugin provides `.delta` method for perceived color difference calculations.
+Also plugin provides `.delta` method for [perceived color difference calculations](https://en.wikipedia.org/wiki/Color_difference#CIEDE2000).
```js
import { colord, extend } from "colord";
@@ -857,8 +856,8 @@ extend([labPlugin]);
colord({ l: 53.24, a: 80.09, b: 67.2 }).toHex(); // "#ff0000"
colord("#ffffff").toLab(); // { l: 100, a: 0, b: 0, alpha: 1 }
-colord("#afafaf").delta("#b4b4b4") // 0.014
-colord("#000").delta("#fff") // 1.0
+colord("#afafaf").delta("#b4b4b4"); // 0.014
+colord("#000000").delta("#ffffff"); // 1
```
diff --git a/src/constants.ts b/src/constants.ts
index 1db803f..fa8f662 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -13,13 +13,3 @@ export const ANGLE_UNITS: Record = {
turn: 360,
rad: 360 / (Math.PI * 2),
};
-
-/**
- * Radians to degrees multiplier.
- */
-export const rad2deg = 180 / Math.PI;
-
-/**
- * Degrees to radiants multiplier.
- */
-export const deg2rad = Math.PI / 180;
\ No newline at end of file
diff --git a/src/get/getPerceivedDifference.ts b/src/get/getPerceivedDifference.ts
index d6a9e55..dfb74e1 100644
--- a/src/get/getPerceivedDifference.ts
+++ b/src/get/getPerceivedDifference.ts
@@ -1,4 +1,3 @@
-import { rad2deg, deg2rad } from "../constants";
import { LabaColor } from "../types";
/**
@@ -14,26 +13,22 @@ import { LabaColor } from "../types";
*
* | Delta E | Perception |
* |---------|----------------------------------------|
- * | <= 1.0 | Not perceptible by human eyes |
- * | 1 - 2 | Perceptible through close observation |
- * | 2 - 10 | Perceptible at a glance |
+ * | <= 1.0 | Not perceptible by human eyes |
+ * | 1 - 2 | Perceptible through close observation |
+ * | 2 - 10 | Perceptible at a glance |
* | 11 - 49 | Colors are more similar than opposite |
- * | 100 | Colors are exact opposite |
+ * | 100 | Colors are exact opposite |
*
* [Source](http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE2000.html)
* [Read about Delta E](https://zschuessler.github.io/DeltaE/learn/#toc-delta-e-2000)
*/
export function getDeltaE00(color1: LabaColor, color2: LabaColor): number {
- /**
- * kl - grafic arts = 1; textiles = 2;
- * kl - unity factor;
- * kh - weighting factor;
- */
- const [kl, kc, kh] = [1, 1, 1];
-
const { l: l1, a: a1, b: b1 } = color1;
const { l: l2, a: a2, b: b2 } = color2;
+ const rad2deg = 180 / Math.PI;
+ const deg2rad = Math.PI / 180;
+
// dc -> delta c;
// ml -> median l;
const c1 = (a1 ** 2 + b1 ** 2) ** 0.5;
@@ -55,13 +50,8 @@ export function getDeltaE00(color1: LabaColor, color2: LabaColor): number {
let h1 = a11 === 0 && b1 === 0 ? 0 : Math.atan2(b1, a11) * rad2deg;
let h2 = a22 === 0 && b2 === 0 ? 0 : Math.atan2(b2, a22) * rad2deg;
- if (h1 < 0) {
- h1 += 360;
- }
-
- if (h2 < 0) {
- h2 += 360;
- }
+ if (h1 < 0) h1 += 360;
+ if (h2 < 0) h2 += 360;
let dh = h2 - h1;
const dhAbs = Math.abs(h2 - h1);
@@ -99,6 +89,10 @@ export function getDeltaE00(color1: LabaColor, color2: LabaColor): number {
const Rc = 2 * (c7 / (c7 + 25 ** 7)) ** 0.5;
const Rt = -Rc * Math.sin(deg2rad * 2 * dTheta);
+ const kl = 1; // 1 for graphic arts, 2 for textiles
+ const kc = 1; // unity factor
+ const kh = 1; // weighting factor
+
return (
((dL / kl / sL) ** 2 +
(dC / kc / sC) ** 2 +
diff --git a/src/plugins/lab.ts b/src/plugins/lab.ts
index 41547ca..1683550 100644
--- a/src/plugins/lab.ts
+++ b/src/plugins/lab.ts
@@ -8,15 +8,16 @@ declare module "../colord" {
interface Colord {
/**
* Converts a color to CIELAB color space and returns an object.
- * The object always includes `alpha` value [0—1].
+ * The object always includes `alpha` value [0, 1].
*/
toLab(): LabaColor;
/**
* Calculates the perceived color difference for two colors according to
* [Delta E2000](https://en.wikipedia.org/wiki/Color_difference#CIEDE2000).
+ * Returns a value in [0, 1] range.
*/
- delta(color: AnyColor | Colord): number;
+ delta(color?: AnyColor | Colord): number;
}
}
@@ -29,7 +30,7 @@ const labPlugin: Plugin = (ColordClass, parsers): void => {
return roundLaba(rgbaToLaba(this.rgba));
};
- ColordClass.prototype.delta = function (color) {
+ ColordClass.prototype.delta = function (color = "#FFF") {
const compared = color instanceof ColordClass ? color : new ColordClass(color);
const delta = getDeltaE00(this.toLab(), compared.toLab()) / 100;
return clamp(round(delta, 3));