please include function showImage.

static ImageSurface showImage_centered(final BufferedImage img) {
  ret (ImageSurface) swing(func {
    ImageSurface is = new ImageSurface(img);
    JPanel panel = new JPanel(new GridBagLayout);
    panel.add(is);
    JFrame frame = showPackedFrame(new JScrollPane(panel));
    frameIcon(frame, showImage_defaultIcon);
    return is;
  });
}

static ImageSurface showImage_centered(final BufferedImage img, fS title) {
  ret setFrameTitle(showImage_centered(img), title);
}

static ImageSurface showImage_centered(S title, BufferedImage img) {
  ret showImage_centered(img, title);
}

static ImageSurface showImage_centered(S title, RGBImage img) {
  return showImage_centered(title, img.getBufferedImage());
}

static ImageSurface showImage_centered(ImageSurface is, BufferedImage img) {
  if (is == null) ret showImage_centered(img);
  is.setImage(img);
  ret is;
}

// make or update the ImageSurface
static ImageSurface showImage_centered(ImageSurface is, S title, BufferedImage img) {
  if (is == null) ret showImage_centered(title, img);
  is.setImage(img);
  setFrameTitle(is, title);
  ret is;
}

static ImageSurface showImage_centered(ImageSurface surface, RGBImage img, S title) {
  ret setFrameTitle(showImage_centered(img, surface), title);
}

static ImageSurface showImage_centered(RGBImage img, ImageSurface surface) {
  if (surface == null)
    ret showImage_centered(img);
  else {
    surface.setImage(img);
    ret surface;
  }
}

static ImageSurface showImage_centered(RGBImage img) {
  return showImage_centered(img.getBufferedImage());
}

static ImageSurface showImage_centered(ImageSurface surface, S title, RGBImage img) {
  ret showImage_centered(surface, img, title);
}