function erasePixel(x, y) {
  const pixel = this.layer.getPixelAt(x, y);
  // nothing to erase
  if (pixel === null) return;
  this.resizeByOffset(x, y);
  this.erasePixelFast(x, y, pixel);
  return;
}
@param {Number} x
@param {Number} y
@return {Void}