JAI bug with negative offset in AffineTransform

Name: wl91122 Date: 07/19/99


I had a couple of different bugs. One was that the application of a clipping
region that intersected the image would cause the image to shift into
the visible portion of the clip. I'm guessing that this one was the
inability to use a negative transform, i.e. one that would translate
the origin of the image to, for example, <-6,-10>. But it's been
awhile.

My image is a png, I don't know if this happens with a non-png.
Here is a test program. Note that I'd expect that negative
translation should work, but it doesn't.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.renderable.ParameterBlock;
import java.awt.image.RenderedImage;
import java.awt.geom.AffineTransform;
import java.util.Vector;
import javax.media.jai.*;

public class JAItester extends JFrame
{
  public static JAItester theApp;

  double scale;
  int srcoffset;
  int dstoffset;
  JLabel scalel, offsetsrcl, offsetdestl;
  RenderedImage image;
  JLabel canvas;

  public JAItester(String filename)
  {
    JPanel panel;
    JButton button;
    JScrollBar scalesb, offsetsrc, offsetdest;
    JPanel p;
    JLabel l;
    JPanel outputpanel;
    
    ParameterBlock pb = new ParameterBlock().add(filename);
    image = (RenderedImage) JAI.create("fileload", pb, null);

    try {
      // Steel L&F
      UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
    } catch (Exception exc) {
      System.err.println("Error loading L&F: " + exc);
      exc.printStackTrace();
    }

    getContentPane().setLayout(new BorderLayout());
    setSize(640,480);

    panel = new JPanel();
    panel.setLayout(new BorderLayout());
    getContentPane().add(panel, BorderLayout.CENTER);

    p = new JPanel();
    p.setLayout(new FlowLayout());
    
    l = new JLabel("Scale factor: ");
    p.add(l);
    scalesb = new JScrollBar(JScrollBar.HORIZONTAL, 10, 1, 1, 50);
    scalesb.setSize(200, 20);
    p.add(scalesb);
    l = new JLabel("Source offset x,y: ");
    p.add(l);
    offsetsrc = new JScrollBar(JScrollBar.HORIZONTAL, 0, 1, 0, 50);
    offsetsrc.setSize(200, 20);
    p.add(offsetsrc);
    l = new JLabel("Destination offset x,y: ");
    p.add(l);
    offsetdest = new JScrollBar(JScrollBar.HORIZONTAL, 0, 1, 0, 50);
    offsetdest.setSize(200, 20);
    p.add(offsetdest);
    panel.add(p, BorderLayout.NORTH);

    p = new JPanel();
    p.setLayout(new FlowLayout());
    scalel = new JLabel("");
    offsetsrcl = new JLabel("");
    offsetdestl = new JLabel("");
    p.add(scalel);
    p.add(offsetsrcl);
    p.add(offsetdestl);
    panel.add(p, BorderLayout.SOUTH);

    canvas = new JLabel("Image Display Area");
    canvas.setSize(150, 150);
    panel.add(canvas, BorderLayout.CENTER);

    scalesb.addAdjustmentListener( new AdjustmentListener() {
      public void adjustmentValueChanged(AdjustmentEvent e) {
scale = (double) e.getValue() / 10.0;
Update();
      }
    });
    offsetsrc.addAdjustmentListener( new AdjustmentListener() {
      public void adjustmentValueChanged(AdjustmentEvent e) {
srcoffset = e.getValue();
Update();
      }
    });
    offsetdest.addAdjustmentListener( new AdjustmentListener() {
      public void adjustmentValueChanged(AdjustmentEvent e) {
dstoffset = e.getValue();
Update();
      }
    });
  }

  public void Update() {
    Graphics2D cg = (Graphics2D) canvas.getGraphics();
    AffineTransform xform;

    // Put new values up
    scalel.setText("Scale factor: " + Double.toString(scale));
    offsetsrcl.setText("Source offset: " + Integer.toString(srcoffset));
    offsetdestl.setText("Dest offset: " + Integer.toString(dstoffset));

    // Clear it
    cg.setBackground(Color.blue);
    cg.clearRect(0, 0, 200, 200);


    // Do it
    xform = new AffineTransform();
    xform.translate((double) dstoffset, (double) dstoffset);
    xform.scale(scale, scale);
    xform.translate((double) -srcoffset, (double) -srcoffset);
    
    cg.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
    cg.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    cg.drawRenderedImage(image, xform);
  }

  /**
   * The main entry point for the application.
   *
   * @param args Array of parameters passed to the application
   * via the command line.
   */
  public static void main(String args[])
  {
    if (args.length < 1) {
      System.err.println("JAItester imagefile");
      System.exit(-1);
    }
    theApp = new JAItester(args[0]);
    theApp.setVisible(true);
  }
}
(Review ID: 53730)
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