No idea of what giCentre could be, but I conservatively move the topic to the Contributed Libraries section, in case it is a library. General advice: don't assume everybody knows all the existing Java libraries, give references or links. This one can probably be easily googled, but easing the work of would be helper is a good step toward solution... (Unless you expect answers only from those knowing the library...)

Sorry, it's http://www.gicentre.org/utils/zoom/

But I would also use another library if something similar exists. Currently I'm thinking about how I have to update the buffered image when zooming, otherwise you can see aliasing effects. Maybe it shouldn't use the buffered image at all while zooming and after zooming ends update the buffer and then take the bufferedImage again (while nothing happens except mousOver effects).

regards,
Johannes

OK, sorry for the rant, I see that library is a new one listed in the official listing, but my advices (updated above) are still valid: making the answer easier improve chances to get an answer! (plus it attracts attention/interest to a new library, increasing number of knowledgeable people on the topic!).

I only quickly scanned the doc you link to, but it looks like listeners use a specific nested class, not some mouseEvent. Ah, I found the mouseEvent in the JavaDoc, but it isn't a callback, it is a method to call yourself. Have you tried to implement the ZoomPanListener?

Jep, I've implemented the ZoomPanListener, but the methods didn't get called.

I've looked through the code and it seems it's

1.     public ZoomPan(PApplet aContext)
2.     {
3.         this.aContext = aContext;
4.         if (aContext == null)
5.         {
6.             System.err.println("Warning: No applet context provided for ZoomPan.");
7.             return;
8.         }
9.         graphics = null;
10.        
11.         listeners = new Vector<ZoomPanListener>();
12.         reset();
13.         aContext.registerMouseEvent(this);
14.         aContext.addMouseWheelListener(new MouseWheelMonitor());
15.     }

Maybe it's the registerMouseEvent(this); which should invoke mouseEvent(event) when the mouse is zooming/dragging? But it seems the method isn't invoked at all and currently I don't know how to invoke it manually. Thus also isZooming() and isPanning() return always false:

1.                 if (mZoomer.isZooming() || mZoomer.isPanning() || mSavePDF) {
2.                     LOGWRAPPER.debug("drawing");
3.                     mParent.background(0, 0, mBackgroundBrightness);
4.                     mParent.translate(mParent.width / 2, mParent.height / 2 + 21);
5.                     mDraw = EDraw.DRAW;
6.                     for (final SunburstItem item : mItems) {
7.                         item.update(mGUI.getMappingMode(), null);
8.                         mDraw.drawStrategy(this, item);
9.                     }
10.                 } else {
11.                     mParent.image(mImg, 0, 0);
12.                     mParent.translate(mParent.width / 2, mParent.height / 2 + 21);
13.                 }

I found the folllowing code in PApplet:

1.   public void registerMouseEvent(Object o) {
2.     Class<?> methodArgs[] = new Class[] { MouseEvent.class };
3.     registerWithArgs(mouseEventMethods, "mouseEvent", o, methodArgs);
4.   }

1.   protected void registerWithArgs(RegisteredMethods meth,
2.                                   String name, Object o, Class<?> cargs[]) {
3.     Class<?> c = o.getClass();
4.     try {
5.       Method method = c.getMethod(name, cargs);
6.       meth.add(o, method);
7.     } catch (NoSuchMethodException nsme) {
8.       die("There is no public " + name + "() method in the class " +
9.           o.getClass().getName());
10.     } catch (Exception e) {
11.       die("Could not register " + name + " + () for " + o, e);
12.     }
13.   }

Thus I assume it should call the method via reflection but it seems it doesn't or something different doesn't work, because I'm using the Processing core library from within Java/Eclipse and the constructor where I'm setting up an instance of the ZoomPane is:

1.     /**
2.      * Private constructor.
3.      *
4.      * @param paramParentApplet
5.      *            parent processing applet
6.      * @param paramModel
7.      *            the model
8.      * @param paramReadDB
9.      *            read database
10.      */
11.     private SunburstGUI(final PApplet paramParentApplet, final SunburstModel paramModel,
12.         final ReadDB paramReadDB) {
13.         mParent = (Embedded)paramParentApplet;
14.         mModel = paramModel;
15.         mZoomer = new ZoomPan(paramParentApplet);
16.         mZoomer.setMouseMask(PConstants.CONTROL);
17.         mZoomer.addZoomPanListener(new MyListener());
18.     }

regards,
johannes

I don't see your MyListener class.
And don't forget it must be nested, ie. it must be a class inside the main PApplet class.

Does it really have to be in the main PApplet class? But I think you're right.

I have a class "Embedded" which extends PApplet and a SunburstGUI class where the GUI/View and draw() is located. Now I've moved

1.         /** Class for responding to the end of a zoom or pan action. */
2.         public class MyListener implements ZoomPanListener {
3.             @Override
4.             public void panEnded() {
5.                 LOGWRAPPER.debug("Pan ended!");
6.                 mGUI.update();
7.             }
8.             @Override
9.             public void zoomEnded() {
10.                 LOGWRAPPER.debug("Zoom ended!");
11.                 mGUI.update();
12.             }
13.         }

to the Embedded class and my constructor in SunburstGUI now looks like:

1.     /**
2.      * Private constructor.
3.      *
4.      * @param paramParentApplet
5.      *            parent processing applet
6.      * @param paramModel
7.      *            the model
8.      * @param paramReadDB
9.      *            read database
10.      */
11.     private SunburstGUI(final PApplet paramParentApplet, final SunburstModel paramModel,
12.         final ReadDB paramReadDB) {
13.         mParent = (Embedded)paramParentApplet;
14.         mModel = paramModel;
15.         mZoomer = new ZoomPan(paramParentApplet);
16.         mZoomer.setMouseMask(PConstants.CONTROL);
17.         mZoomer.addZoomPanListener(mParent.new MyListener());
18.     }

Pan ended or Zoom ended is never printed out :-/

Furthermore isZooming and isPanning, which should work without the listener are never set to true.

Well, I had to call mouseEvent(event) inside mousePressed(...):

1.     public void mousePressed(final MouseEvent paramEvent) {
2.         mControlP5.controlWindow.mouseEvent(paramEvent);
3.         mZoomer.mouseEvent(paramEvent);
4.         ...
5.     }

One more thing is how to update the buffered image after a zoom or pan. At first I thought I just can copy the whole window into the image, but that fails on a mouseOver (I just want to copy the whole background with the sunburst items). Thus I think I have to transform exactly like it's done with mZoomer.transform(), so I would have to duplicate the whole code but use PGraphics instead of PApplet on which to do the transformation/scaling :-/