colour-tool/Colour/convert/HWB2RGB.js

dev-tool that makes colours easier to deal with

require('../mathExtension')();

module.exports = (H,W,B) => {
    // scale W and B channels from [0,100] to [0,1];
    H /= 60;
    W /= 100;
    B /= 100;

    // W + B <= 1 to return valid Red, Green, Blue values
    const sumWB = W + B;
    if(sumWB > 1) {
        W /= sumWB;
        B /= sumWB;
    }

    const v = 1 - B;
    if (H === undefined) return [v,v,v];

    const i = Math.floor(H)
    const f = (i % 2 === 1)? 1 - (H - i) : H - i // test if i is odd
    const n = W + f * (1 - sumWB);
    
    switch(i) {
        case 0: return [v, n, W].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
        case 1: return [n, v, W].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
        case 2: return [W, v, n].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
        case 3: return [W, n, v].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
        case 4: return [n, W, v].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
        case 5: return [v, W, n].map(value => Math.round(value * 255)).map(channel => channel < 0 ? 0:channel);
    }
}