Zooming an image and scrolling it using a JScrollPane

Question

Hi all, I know this is one of the most common problems in this forum but i cant get any of the replys to work in my code.
The problem:
I create an image with varying pixel colors depending on the value obtained from an AbstractTableModel and display it to the screen.
I then wish to be able to zoom in on the image and make it scrollable as required.
At the minute the scrolling method is working but only when i resize or un-focus and re-focus the JInternalFrame. Ive tried calling revalidate (and various other options) on the JScrollPane within the paintComponents(Graphics g) method but all to no avail.
Has anyone out there any ideas cause this is melting my head!
Heres the code im using (instance is called and added to a JDesktopPane):
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.geom.AffineTransform;
import uk.ac.qub.mvda.gui.MVDATableModel;
import uk.ac.qub.mvda.utils.MVDAConstants;
public class HCLSpectrumPlot extends JInternalFrame implements MVDAConstants
  AbstractAction zoomInAction = new ZoomInAction();
  AbstractAction zoomOutAction = new ZoomOutAction();
  double zoomFactorX = 1.0;
  double zoomFactorY = 1.0;
  private AffineTransform theTransform;
  private ImagePanel imageViewerPanel;
  private JScrollPane imageViewerScroller;
  public HCLSpectrumPlot(String title, MVDATableModel model)
    super(title, true, true, true, true);
    int imageHeight_numOfRows = model.getRowCount();
    int imageWidth_numOfCols = model.getColumnCount();
    int numberOfColourBands = 3;
    double maxValueInTable = 0;
    double[][] ValueAtTablePosition =
        new double[imageHeight_numOfRows][imageWidth_numOfCols];
    for(int i=0; i<imageHeight_numOfRows; i++)
      for(int j=0; j<imageWidth_numOfCols; j++)
     ValueAtTablePosition[i][j] = ((Double)model.getValueAt
             (i,j)).doubleValue();
    for(int i=0; i<imageHeight_numOfRows; i++)
      for(int j=0; j<imageWidth_numOfCols; j++)
     if ( ValueAtTablePosition[i][j] > maxValueInTable)
       maxValueInTable = ValueAtTablePosition[i][j];
    BufferedImage newImage = new BufferedImage(imageWidth_numOfCols,
          imageHeight_numOfRows, BufferedImage.TYPE_3BYTE_BGR);
    WritableRaster newWritableImage = newImage.getRaster();
    int colourB;
    double pixelValue, cellValue, newPixelValue;
    for (int x = 0; x < imageHeight_numOfRows; x++)
      for (int y = 0; y < imageWidth_numOfCols; y++)
     colourB = 0;
     cellValue = ValueAtTablePosition[x][y];
     pixelValue = (1 - (cellValue / maxValueInTable)) * 767;
     pixelValue = pixelValue - 256;
     while (colourB < numberOfColourBands)
       if ( pixelValue < 0 )
         newPixelValue = 256 + pixelValue;
         newWritableImage.setSample(x, y, colourB, newPixelValue);
         colourB++;
            while ( colourB < numberOfColourBands )
           newWritableImage.setSample(x, y, colourB, 0);
           colourB++;
     else
       newWritableImage.setSample(x, y, colourB, 255);
     colourB++;
     pixelValue = pixelValue - 256;
      }//while
     }//for-y
    }//for-x
    imageViewerPanel = new ImagePanel(this, newImage);
    imageViewerScroller =     new JScrollPane(imageViewerPanel,
                        JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
               JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
    this.getContentPane().setLayout(new BorderLayout());
    this.getContentPane().add(imageViewerScroller, BorderLayout.CENTER);
    JToolBar editTools = new JToolBar();
    editTools.setOrientation(JToolBar.VERTICAL);
    editTools.add(zoomInAction);
    editTools.add(zoomOutAction);
    this.getContentPane().add(editTools, BorderLayout.WEST);
    this.setVisible(true);
  class ImagePanel extends JPanel
    private int iWidth, iHeight;
    private int i=0;
    private BufferedImage bufferedImageToDisplay;
    private JInternalFrame parentFrame;
    public ImagePanel(JInternalFrame parent, BufferedImage image)
      super();
      parentFrame = parent;
      bufferedImageToDisplay = image;
      iWidth = bufferedImageToDisplay.getWidth();
      iHeight = bufferedImageToDisplay.getHeight();
      theTransform = new AffineTransform();
      //theTransform.setToScale(parent.getContentPane().getWidth(),
                                parent.getContentPane().getHeight());
      this.setPreferredSize(new Dimension(iWidth, iHeight));
    }//Constructor
    public void paintComponent(Graphics g)
      super.paintComponent(g);
      ((Graphics2D)g).drawRenderedImage(bufferedImageToDisplay,
                                         theTransform);
      this.setPreferredSize(new Dimension((int)(iWidth*zoomFactorX),
                                      (int)(iHeight*zoomFactorY)));
    }//paintComponent
  }// end class ImagePanel
   * Class to handle a zoom in event
   * @author Ross McCaughrain
   * @version 1.0
  class ZoomInAction extends AbstractAction
   * Default Constructor.
  public ZoomInAction()
    super(null, new ImageIcon(HCLSpectrumPlot.class.getResource("../"+
              MVDAConstants.PATH_TO_IMAGES + "ZoomIn24.gif")));
    this.putValue(Action.SHORT_DESCRIPTION,"Zooms In on the Image");
    this.setEnabled(true);
  public void actionPerformed(ActionEvent e)
    zoomFactorX += 0.5;
    zoomFactorY += 0.5;
    theTransform = AffineTransform.getScaleInstance(zoomFactorX,
                                                zoomFactorY);
    repaint();
  // ZoomOut to be implemented
}// end class HCLSpectrumPlotAll/any help greatly appreciated! thanks for your time.
RossMcC

Answer 1

Small mistake, the revalidate must be called on the panel not on the jsp.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class UsaZ extends JFrame 
     IPanel      panel = new IPanel();
     JScrollPane jsp   = new JScrollPane(panel);
public UsaZ() 
     addWindowListener(new WindowAdapter()
     addWindowListener(new WindowAdapter()
     {     public void windowClosing(WindowEvent ev)
          {     dispose();
               System.exit(0);
     setBackground(Color.lightGray);
     getContentPane().add("Center",jsp);
     setBounds(1,1,400,320);
     setVisible(true);
public class IPanel extends JComponent
     Image  map;
     double zoom = 1;
     double iw;
     double ih;
public IPanel()
     map = getToolkit().createImage("us.gif");
     MediaTracker tracker = new MediaTracker(this);
     tracker.addImage(map,0);
     try {tracker.waitForID(0);}
     catch (InterruptedException e){}
     iw = map.getWidth(this);
     ih = map.getHeight(this);
     zoom(0);     
     addMouseListener(new MouseAdapter()     
     {     public void mouseReleased(MouseEvent m)
               zoom(0.04);               
               repaint();      
               revalidate();
public void zoom(double z)
     zoom = zoom + z;
     setPreferredSize(new Dimension((int)(iw*zoom)+2,(int)(ih*zoom)+2));
public void paintComponent(Graphics g)
     super.paintComponent(g);
     Graphics2D g2 = (Graphics2D)g;
     g2.scale(zoom,zoom);
     g2.drawImage(map,1,1,null);
     g.drawRect(0,0,map.getWidth(this)+1,map.getHeight(this)+1);
public static void main (String[] args) 
      new UsaZ();
[/cdoe]
Noah