TypeScript RGBA to RGB

rgbaToRgb.ts

interface RGBAtoRGBOptions {
  toColorRGBA: string;
  backgroundColorRGB?: string;
}

function rgbaToRgb({ toColorRGBA, backgroundColorRGB = 'rgb(255,255,255)' }: RGBAtoRGBOptions) {
  const [r, g, b, a] = toColorRGBA
    .replace(/rgba|\(|\)/g, '')
    .split(',')
    .map((str) => parseInt(str, 2));
  const [bgR, bgG, bgB] = backgroundColorRGB
    .replace(/rgb|\(|\)/g, '')
    .split(',')
    .map((str) => parseInt(str, 2));

  const r3 = Math.round((1 - a) * bgR + a * r);
  const g3 = Math.round((1 - a) * bgG + a * g);
  const b3 = Math.round((1 - a) * bgB + a * b);

  return `rgb(${r3},${g3},${b3})`;
}