lib-colors/src/hsl/helpers/hsl_to_rgb.helper.ts

Simple node.js library for work with colors

import type { IRGB } from '../../rgb/rgb.interface';
import type { IHSL } from '../hsl.interface';

export function hslToRgb(hsl: IHSL): IRGB {
  const { h, s, l, a } = { ...hsl };

  let r: number, g: number, b: number;

  if (s === 0) {
    r = g = b = l;
  } else {
    const q = l < 0.5 ? l * (1 + s) : l + s - l * s;
    const p = 2 * l - q;
    const hue = h / 360;

    r = hue2rgb(p, q, hue + 1 / 3);
    g = hue2rgb(p, q, hue);
    b = hue2rgb(p, q, hue - 1 / 3);
  }

  return {
    r: Math.round(r * 255),
    g: Math.round(g * 255),
    b: Math.round(b * 255),
    a,
  };
}

function hue2rgb(p: number, q: number, t: number): number {
  if (t < 0) t += 1;
  if (t > 1) t -= 1;
  if (t < 1 / 6) return p + (q - p) * 6 * t;
  if (t < 1 / 2) return q;
  if (t < 2 / 3) return p + (q - p) * (2 / 3 - t) * 6;
  return p;
}