chroma-js/src/io/hex/rgb2hex.js

JavaScript library for color conversions

import { unpack, last } from '../../utils/index.js';
const { round } = Math;

const rgb2hex = (...args) => {
    let [r, g, b, a] = unpack(args, 'rgba');
    let mode = last(args) || 'auto';
    if (a === undefined) a = 1;
    if (mode === 'auto') {
        mode = a < 1 ? 'rgba' : 'rgb';
    }
    r = round(r);
    g = round(g);
    b = round(b);
    const u = (r << 16) | (g << 8) | b;
    let str = '000000' + u.toString(16); //#.toUpperCase();
    str = str.substr(str.length - 6);
    let hxa = '0' + round(a * 255).toString(16);
    hxa = hxa.substr(hxa.length - 2);
    switch (mode.toLowerCase()) {
        case 'rgba':
            return `#${str}${hxa}`;
        case 'argb':
            return `#${hxa}${str}`;
        default:
            return `#${str}`;
    }
};

export default rgb2hex;