@spellix/magic-color-transformer/src/meta/lab.ts

Magic color transform library

/* eslint-disable -- allow for magic-color */
import type { HexColor, HsbColor, HslColor, LabColor, RgbColor } from '../types';
import { rgbToHex, rgbToHsb, rgbToHsl } from './rgb';

const labRegex =
  /^lab\(\s*(100|[1-9]?\d(?:\.\d+)?)\s+(-?(?:1[01]\d|12[0-8]|\d?\d)(?:\.\d+)?)\s+(-?(?:1[01]\d|12[0-8]|\d?\d)(?:\.\d+)?)(?:\s*\/\s*(0|0?\.\d+|1(?:\.0)?))?\s*\)$/;

export function isLab(color: string): boolean {
  return labRegex.test(color);
}

export function parseLab(color: string): { values: LabColor; alpha: number } {
  const match = labRegex.exec(color);

  if (!match) throw new Error('Invalid Lab color format.');
  // @ts-expect-error - allow for magic-color
  const lab = [Number.parseFloat(match[1]), Number.parseFloat(match[2]), Number.parseFloat(match[3])] as LabColor;
  const alpha = match[4] ? Number.parseFloat(match[4]) : 1;

  return { values: lab, alpha };
}

function xyz_rgb(r: number) {
  r = 255 * (r <= 0.003_04 ? 12.92 * r : 1.055 * r ** (1 / 2.4) - 0.055);

  return Math.min(Math.max(0, r), 255);
  // return 255 * (r <= 0.00304 ? 12.92 * r : 1.055 * r ** (1 / 2.4) - 0.055)
}

function lab_xyz(t: number) {
  return t > 0.206_896_552 ? t * t * t : 0.128_418_55 * (t - 0.137_931_034);
}

export function labToRgb(color: LabColor): RgbColor {
  const [l, a, b] = color;
  let x;
  let y;
  let z;

  y = (l + 16) / 116;
  x = y + a / 500;
  z = y - b / 200;

  y = Number(lab_xyz(y));
  x = 0.950_47 * lab_xyz(x);
  z = 1.088_83 * lab_xyz(z);

  const r = xyz_rgb(3.240_454_2 * x - 1.537_138_5 * y - 0.498_531_4 * z); // D65 -> sRGB
  const g = xyz_rgb(-0.969_266 * x + 1.876_010_8 * y + 0.041_556 * z);
  const b_ = xyz_rgb(0.055_643_4 * x - 0.204_025_9 * y + 1.057_225_2 * z);

  return [r, g, b_];
}

export function labToHex(color: LabColor): HexColor {
  return rgbToHex(labToRgb(color));
}

export function labToHsl(color: LabColor): HslColor {
  return rgbToHsl(labToRgb(color));
}

export function labToHsb(color: LabColor): HsbColor {
  return rgbToHsb(labToRgb(color));
}