Swing/ZoomAndPanPanel のバックアップ(No.1)

class ZoomAndPanePanel extends JPanel {
  private final AffineTransform coordTransform = new AffineTransform();
  private final transient Image img;
  private final Rectangle imgrect;
  private transient ZoomAndPanHandler handler;

  public ZoomAndPanePanel(Image img) {
    super();
    this.img = img;
    this.imgrect = new Rectangle(img.getWidth(null), img.getHeight(null));
  }
  @Override public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setPaint(new Color(0x55FF0000, true));

    //AffineTransform at = g2.getTransform();
    //at.concatenate(coordTransform);
    //g2.setTransform(at);
    //g2.drawImage(img, 0, 0, this);
    //g2.fill(new Rectangle(500, 140, 150, 150));

    //g2.drawRenderedImage((java.awt.image.RenderedImage) img, coordTransform);
    g2.drawImage(img, coordTransform, this);
    g2.fill(coordTransform.createTransformedShape(new Rectangle(500, 140, 150, 150)));

    g2.dispose();
  }
  @Override public Dimension getPreferredSize() {
    Rectangle r = coordTransform.createTransformedShape(imgrect).getBounds();
    return new Dimension(r.width, r.height);
  }
  @Override public void updateUI() {
    removeMouseListener(handler);
    removeMouseMotionListener(handler);
    removeMouseWheelListener(handler);
    super.updateUI();
    handler = new ZoomAndPanHandler();
    addMouseListener(handler);
    addMouseMotionListener(handler);
    addMouseWheelListener(handler);
  }

  protected class ZoomAndPanHandler extends MouseAdapter {
    private static final int MIN_ZOOM = -9;
    private static final int MAX_ZOOM = 16;
    private static final int EXTENT = 1;
    private final BoundedRangeModel zoomRange = new DefaultBoundedRangeModel(
        0, EXTENT, MIN_ZOOM, MAX_ZOOM + EXTENT);
    private final Point dragStartPoint = new Point();
    @Override public void mousePressed(MouseEvent e) {
      dragStartPoint.setLocation(e.getPoint());
    }
    @Override public void mouseDragged(MouseEvent e) {
      Point dragEndPoint = e.getPoint();
      Point dragStart = inversedPoint(dragStartPoint);
      Point dragEnd   = inversedPoint(dragEndPoint);
      coordTransform.translate(dragEnd.x - dragStart.x, dragEnd.y - dragStart.y);
      dragStartPoint.setLocation(dragEndPoint);
      e.getComponent().repaint();
    }
    @Override public void mouseWheelMoved(MouseWheelEvent e) {
      int dir = e.getWheelRotation();
      int z = zoomRange.getValue();
      zoomRange.setValue(z + EXTENT * (dir > 0 ? -1 : 1));
      if (z != zoomRange.getValue()) {
        Container c = SwingUtilities.getAncestorOfClass(
            JViewport.class, e.getComponent());
        if (c instanceof JViewport) {
          Rectangle r = ((JViewport) c).getBounds();
          Point p = new Point(r.x + r.width / 2, r.y + r.height / 2);
          Point p1 = inversedPoint(p);

          double s = 1d + zoomRange.getValue() * .1;
          coordTransform.setToScale(s, s);

          Point p2 = inversedPoint(p);
          coordTransform.translate(p2.getX() - p1.getX(), p2.getY() - p1.getY());

          c.revalidate();
          c.repaint();
        }
      }
    }
    //https://community.oracle.com/thread/1263955
    //How to implement Zoom & Pan in Java using Graphics2D
    private Point inversedPoint(Point p1) {
      Point p2 = new Point();
      try {
        AffineTransform inverse = coordTransform.createInverse();
        inverse.transform(p1, p2);
      } catch (NoninvertibleTransformException ex) {
        ex.printStackTrace();
      }
      return p2;
    }
    public AffineTransform getCoordTransform() {
      return coordTransform;
    }
  }
}