Java SE (Java Platform, Standard Edition)

Hi,
I wanted to show an image in a ScrollPane and allow zooming on it with the mouse weel. I am not completely happy with the result as it appears that zooming creates some unwanted vertical and horizontal steps in the image position when the scroll bars are not located on top and left.

For example I expect that the bottom/right pixel of the image will always be visible on the bottom/right position of the ScrollPane when scroll bars are at bottom and right. In my case it is not the case... I already looked at threads here but I don't see exactly the same situation (sometimes not showing ImageView sometimes not about zooming...). I am wondering if I don't just do a stupid mistake.

I give you the code here. Many thanks for your help.

import javafx.application.Application;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.ScrollEvent;
import javafx.stage.Stage;

public class ZoomExample extends Application {

	private ImageView imageView;
	private ScrollPane scrollPane;
	private DoubleProperty zoom;

	@Override
	public void start(Stage primaryStage) throws Exception {
		zoom = new SimpleDoubleProperty(200);
		InvalidationListener listener = new InvalidationListener() {
			@Override
			public void invalidated(Observable arg0) {
				imageView.setFitWidth(zoom.get()*4);
				imageView.setFitHeight(zoom.get()*3);
				scrollPane.requestLayout();
			}
		};
		zoom.addListener(listener);

		scrollPane = new ScrollPane() {
	        @Override
	        protected void layoutChildren() {
	            super.layoutChildren();
	    		System.out.println("Zoom="+zoom.doubleValue()+" Bounds="+getViewportBounds());
	        }
		};
		scrollPane.setPannable(true);
		scrollPane.addEventFilter(ScrollEvent.ANY,
				new EventHandler<ScrollEvent>() {
					@Override
					public void handle(ScrollEvent event) {
						if (event.getDeltaY() > 0) {
							zoom.set(zoom.get() * 1.1);
						} else if (event.getDeltaY() < 0) {
							zoom.set(zoom.get() / 1.1);
						}
						event.consume();
					}
				});
		imageView = new ImageView(new Image("myImage.jpg")) {{
			setPreserveRatio(true);
		}};
		scrollPane.setContent(imageView);
		Scene scene = new Scene(scrollPane, zoom.get()*4, zoom.get()*3);
		primaryStage.setScene(scene);
		primaryStage.show();
		imageView.setFitWidth(zoom.get()*4);
		imageView.setFitHeight(zoom.get()*3);
		scrollPane.setHvalue(scrollPane.getHmax());
		scrollPane.setVvalue(scrollPane.getVmax());
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		launch(args);
	}

}