thats not true!

It enough if component just set properly his preferredSize.
Scrollable is for _complex_ components which need
_fine_grained_scroll_control_.

example below:

public class ImagePanel extends JPanel {

   Image img;

   public ImagePanel(Image img) {
       this.img = img;
   }

   public Dimension getPreferredSize() {
       if(img == null) return super.getPreferredSize();
       int w = img.getWidth(null);
       int h = img.getHeight(null);
       return new Dimension(w, h);
   }

   public void paintComponent(Graphics g) {
       g.setColor(getBackground());
       g.fillRect(0,0,getWidth(), getHeight());
       if(img != null) {
           g.drawImage(img, 0, 0, null);
       }
   }

   public static void main(String [] args) {
       JFrame frame = new JFrame();
       Image img = Toolkit.getDefaultToolkit().getImage(...);
       ImagePanel panel = new ImagePanel(img);
       frame.getContentpane().setLayout(new BorderLayout());
       frame.getContentPane().add(panel);
       frame.pack();
       frame.show();
   }
}

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