Code
class ZoomAndPanePanel extends JPanel {
private final AffineTransform zoomTransform = new AffineTransform();
private final transient Image img;
private final Rectangle imgrect;
private transient ZoomHandler handler;
private transient DragScrollListener listener;
protected ZoomAndPanePanel(Image img) {
super();
this.img = img;
this.imgrect = new Rectangle(img.getWidth(this), img.getHeight(this));
}
@Override protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setPaint(new Color(0x55FF0000, true));
Rectangle r = new Rectangle(500, 140, 150, 150);
//use: AffineTransform#concatenate(...) and Graphics2D#setTransform(...)
//https://docs.oracle.com/javase/8/docs/api/java/awt/geom/AffineTransform.html#concatenate-java.awt.geom.AffineTransform-
//AffineTransform at = g2.getTransform();
//at.concatenate(zoomTransform);
//g2.setTransform(at);
//g2.drawImage(img, 0, 0, this);
//g2.fill(r);
//or use: Graphics2D#drawImage(Image, AffineTransform, ImageObserver)
//https://docs.oracle.com/javase/8/docs/api/java/awt/Graphics2D.html#drawImage-java.awt.Image-java.awt.geom.AffineTransform-java.awt.image.ImageObserver-
g2.drawImage(img, zoomTransform, this); //or: g2.drawRenderedImage((RenderedImage) img, zoomTransform);
g2.fill(zoomTransform.createTransformedShape(r));
//BAD EXAMPLE
//g2.setTransform(zoomTransform);
//g2.drawImage(img, 0, 0, this);
g2.dispose();
}
@Override public Dimension getPreferredSize() {
Rectangle r = zoomTransform.createTransformedShape(imgrect).getBounds();
return new Dimension(r.width, r.height);
}
@Override public void updateUI() {
removeMouseListener(listener);
removeMouseMotionListener(listener);
removeMouseWheelListener(handler);
super.updateUI();
listener = new DragScrollListener();
addMouseListener(listener);
addMouseMotionListener(listener);
handler = new ZoomHandler();
addMouseWheelListener(handler);
}
protected class ZoomHandler extends MouseAdapter {
private static final double ZOOM_MULTIPLICATION_FACTOR = 1.2;
private static final int MIN_ZOOM = -10;
private static final int MAX_ZOOM = 10;
private static final int EXTENT = 1;
private final BoundedRangeModel zoomRange = new DefaultBoundedRangeModel(
0, EXTENT, MIN_ZOOM, MAX_ZOOM + EXTENT);
@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()) {
Component c = e.getComponent();
Container p = SwingUtilities.getAncestorOfClass(JViewport.class, c);
if (p instanceof JViewport) {
JViewport vport = (JViewport) p;
Rectangle ovr = vport.getViewRect();
double s = dir > 0 ? 1d / ZOOM_MULTIPLICATION_FACTOR : ZOOM_MULTIPLICATION_FACTOR;
zoomTransform.scale(s, s);
//double s = 1d + zoomRange.getValue() * .1;
//zoomTransform.setToScale(s, s);
Rectangle nvr = AffineTransform.getScaleInstance(s, s).createTransformedShape(ovr).getBounds();
Point vp = nvr.getLocation();
vp.translate((nvr.width - ovr.width) / 2, (nvr.height - ovr.height) / 2);
vport.setViewPosition(vp);
c.revalidate();
c.repaint();
}
}
}
}
}
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