@IBAction func showImg1(_ sender: Any) {
  let image0 = UIImage(named: "Image")

  // ここで初期化しておかないとZoomがおかしくなる
  scrollView.zoomScale = 1

  imageView.image = image0
  imageView.frame.size = image0!.size
  scrollView.contentSize = image0!.size

  adjustImageFitInScrollView()
}