function getRelativePixelAt(x, y) {
  // normalize coordinates
  const bw = this.bounds.w;
  const bh = this.bounds.h;
  const xx = x - this.bounds.x;
  const yy = y - this.bounds.y;
  // check if point inside boundings
  if (
    (xx < 0 || yy < 0) ||
    (bw <= 0 || bh <= 0) ||
    (xx >= bw || yy >= bh)
  ) return (null);
  // search for the pixel at given layer
  const layer = this.getCurrentLayer();
  if (layer !== null) {
    return (layer.getPixelAt(x, y));
  }
  return (null);
}
Get layer relative pixel
@param {Number} x
@param {Number} y
@return {Array}