Convert HSL to RGB colors - helpers - javascript

hslToRgb.js

const hueToRgb = (p, q, t) => {
  let tlocal = t;
  if (tlocal < 0) tlocal += 1;
  if (tlocal > 1) tlocal -= 1;
  if (tlocal < 1 / 6) return p + (q - p) * 6 * tlocal;
  if (tlocal < 1 / 2) return q;
  if (tlocal < 2 / 3) return p + (q - p) * (2 / 3 - tlocal) * 6;

  return p;
};

/*
 * Converts HSL values to RGB values.
 * Expects the following input:
 *  - 'hue' within the [0, 360] range.
 *  - 'saturation' within the [0, 100] range.
 *  - 'lightness' within the [0, 100] range.
 */
export const hslToRgb = (hue, saturation, lightness) => {
  if (saturation === 0) {
    return {
      red: lightness,
      green: lightness,
      blue: lightness,
    };
  }

  const h = hue / 360;
  const l = lightness / 100;
  const s = saturation / 100;

  const q = l < 0.5 ? l * (1 + s) : l + s - l * s;
  const p = 2 * l - q;

  return {
    red: Math.round(hueToRgb(p, q, h + 1 / 3) * 255),
    green: Math.round(hueToRgb(p, q, h) * 255),
    blue: Math.round(hueToRgb(p, q, h - 1 / 3) * 255),
  };
};