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/**
* @preserve
* Copyright 2015-2018 Igor Bezkrovnyi
* All rights reserved. (MIT Licensed)
*
* cie94.ts - part of Image Quantization Library
*/
import { AbstractDistanceCalculator } from './distanceCalculator';
import { rgb2lab } from '../conversion/rgb2lab';
import { inRange0to255 } from '../utils/arithmetic';
/**
* CIE94 method of delta-e
* http://en.wikipedia.org/wiki/Color_difference#CIE94
*/
export abstract class AbstractCIE94 extends AbstractDistanceCalculator {
/**
* Weight in distance: 0.25
* Max DeltaE: 100
* Max DeltaA: 255
*/
declare protected _kA: number;
declare protected _Kl: number;
declare protected _K1: number;
declare protected _K2: number;
calculateRaw(
r1: number,
g1: number,
b1: number,
a1: number,
r2: number,
g2: number,
b2: number,
a2: number,
) {
const lab1 = rgb2lab(
inRange0to255(r1 * this._whitePoint.r),
inRange0to255(g1 * this._whitePoint.g),
inRange0to255(b1 * this._whitePoint.b),
);
const lab2 = rgb2lab(
inRange0to255(r2 * this._whitePoint.r),
inRange0to255(g2 * this._whitePoint.g),
inRange0to255(b2 * this._whitePoint.b),
);
const dL = lab1.L - lab2.L;
const dA = lab1.a - lab2.a;
const dB = lab1.b - lab2.b;
const c1 = Math.sqrt(lab1.a * lab1.a + lab1.b * lab1.b);
const c2 = Math.sqrt(lab2.a * lab2.a + lab2.b * lab2.b);
const dC = c1 - c2;
let deltaH = dA * dA + dB * dB - dC * dC;
deltaH = deltaH < 0 ? 0 : Math.sqrt(deltaH);
const dAlpha = (a2 - a1) * this._whitePoint.a * this._kA;
// TODO: add alpha channel support
return Math.sqrt(
(dL / this._Kl) ** 2 +
(dC / (1.0 + this._K1 * c1)) ** 2 +
(deltaH / (1.0 + this._K2 * c1)) ** 2 +
dAlpha ** 2,
);
}
}
export class CIE94Textiles extends AbstractCIE94 {
protected _setDefaults() {
this._Kl = 2.0;
this._K1 = 0.048;
this._K2 = 0.014;
this._kA = (0.25 * 50) / 255;
}
}
export class CIE94GraphicArts extends AbstractCIE94 {
protected _setDefaults() {
this._Kl = 1.0;
this._K1 = 0.045;
this._K2 = 0.015;
this._kA = (0.25 * 100) / 255;
}
}