/**
 * @preserve
 * Copyright 2015-2016 Igor Bezkrovnyi
 * All rights reserved. (MIT Licensed)
 *
 * cmetric.ts - part of Image Quantization Library
 */
import { AbstractDistanceCalculator } from "./abstractDistanceCalculator"

/**
 * TODO: Name it: http://www.compuphase.com/cmetric.htm
 */
export class CMETRIC extends AbstractDistanceCalculator {
    calculateRaw(r1 : number, g1 : number, b1 : number, a1 : number, r2 : number, g2 : number, b2 : number, a2 : number) : number {
        const rmean = (r1 + r2) / 2 * this._whitePoint.r,
              r     = (r1 - r2) * this._whitePoint.r,
              g     = (g1 - g2) * this._whitePoint.g,
              b     = (b1 - b2) * this._whitePoint.b,
              dE    = ((((512 + rmean) * r * r) >> 8) + 4 * g * g + (((767 - rmean) * b * b) >> 8)),
              dA    = (a2 - a1) * this._whitePoint.a;

        return Math.sqrt(dE + dA * dA);
    }
}