FULL PRODUCT VERSION :
java version "1.6.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta-b59g)
Java HotSpot(TM) Client VM (build 1.6.0-beta-b59g, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
In XOR mode, calling the method

Graphics2D.drawImage(Image img, int x, int y,
                                             int width, int height,
                                             ImageObserver observer);

with a "width" and/or "height" argument smaller than the actual size of the image produces an exception.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Compile the attached program:
     javac -classpath . ImageXOR.java
 
2. Run:
   java -classpath . ImageXOR

==> You should see an exception in the console.

Release Regression From : 5.0
The above release value was the last known release where this bug was non-existent. Since then there has been a regression.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
An image should be drawn in XOR mode.
ACTUAL -
An exception occurs each time Graphics.drawImage is called (see stack below).

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "AWT-EventQueue-0" java.lang.InternalError: Cannot construct MaskBlit for XOR mode
        at sun.java2d.loops.MaskBlit.makePrimitive(Unknown Source)
        at sun.java2d.loops.GraphicsPrimitiveMgr.locate(Unknown Source)
        at sun.java2d.loops.MaskBlit.locate(Unknown Source)
        at sun.java2d.loops.MaskBlit.getFromCache(Unknown Source)
        at sun.java2d.pipe.DrawImage.renderImageXform(Unknown Source)
        at sun.java2d.pipe.DrawImage.transformImage(Unknown Source)
        at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
        at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
        at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
        at sun.awt.image.ImageRepresentation.drawToBufImage(Unknown Source)
        at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
        at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
        at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
        at ImageXOR$1.paint(ImageXOR.java:95)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JLayeredPane.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paintToOffscreen(Unknown Source)
        at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
        at javax.swing.RepaintManager.paint(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source)
        at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source)
        at sun.awt.SunGraphicsCallback.runComponents(Unknown Source)
        at java.awt.Container.paint(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source)
        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown S
ource)
        at java.awt.event.InvocationEvent.dispatch(Unknown Source)
        at java.awt.EventQueue.dispatchEvent(Unknown Source)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.run(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.net.URL;

import javax.swing.JFrame;
import javax.swing.JComponent;
import javax.swing.SwingUtilities;
import java.awt.MediaTracker;

/**
 * Demonstrates a regression concerning the drawing
 * of images in XOR mode.
 *
 * Compile:
 * javac -classpath . ImageXOR.java
 *
 * Run:
 * java -classpath . ImageXOR
 *
 * Stack trace of the exception:
 * Exception in thread "AWT-EventQueue-0" java.lang.InternalError:
 * Cannot construct MaskBlit for XOR mode
 * at sun.java2d.loops.MaskBlit.makePrimitive(Unknown Source)
 * at sun.java2d.loops.GraphicsPrimitiveMgr.locate(Unknown Source)
 * at sun.java2d.loops.MaskBlit.locate(Unknown Source)
 * at sun.java2d.loops.MaskBlit.getFromCache(Unknown Source)
 * at sun.java2d.pipe.DrawImage.renderImageXform(Unknown Source)
 * at sun.java2d.pipe.DrawImage.transformImage(Unknown Source)
 * at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
 * at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
 * at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
 * at sun.awt.image.ImageRepresentation.drawToBufImage(Unknown Source)
 * at sun.java2d.pipe.DrawImage.scaleImage(Unknown Source)
 * at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
 * at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
 * at ImageXOR.paint(ImageXOR.java:49)
 * at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
 * at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
 * at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source)
 * at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source)
 * at java.awt.event.InvocationEvent.dispatch(Unknown Source)
 * at java.awt.EventQueue.dispatchEvent(Unknown Source)
 *
 * Platform information:
 * > java -version
 * java version "1.6.0-beta"
 * Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta-b59g)
 * Java HotSpot(TM) Client VM (build 1.6.0-beta-b59g, mixed mode, sharing)
 *
 * OS: Windows XP SP2.
 *
 * The same code works fine with previous versions of the JDK (for instance 1.5).
 */
public class ImageXOR
  extends JFrame
{
  public ImageXOR()
  {
    final Image img = loadImage();
    
    if (img == null)
      return;
    
    getContentPane().add(new JComponent() {
      public void paint(Graphics g) {
        if (img == null)
          return;
        
        g.setColor(Color.green);
        g.setXORMode(Color.white);
        
        int width = getWidth();
        int height = getHeight();
        
        g.fillRect(0, 0, width, height);
        
        int wImage = img.getWidth(null);
        int hImage = img.getHeight(null);
        
        int x = (width - wImage) / 2;
        int y = (height - hImage) / 2;
        
        // This version of Graphics.drawImage works fine:
        // g.drawImage(img, x, y, null);
        //
        // This version of Graphics.drawImage works fine if
        // width and height are those of the image (49x38 in this example):
        // g.drawImage(img, x, y, wImage, hImage, null);
        //
        // This version of Graphics.drawImage produces the exception
        // "java.lang.InternalError:
        // Cannot construct MaskBlit for XOR mode"
        // at sun.java2d.loops.MaskBlit.makePrimitive(Unknown Source)"
        // with width/height different than those of the image
        // (49x38 in this example):
        g.drawImage(img, x, y, wImage - 1, hImage - 1, null);
      }
    });
  }
  
  // loads the image
  private Image loadImage()
  {
    URL url = getClass().getResource("image.png");
    if (url == null) {
      System.out.println("null URL");
      return null;
    }
    Image img = getToolkit().createImage(url);
    
    final MediaTracker tracker = new MediaTracker(this);
    tracker.addImage(img, 0);
    try {
      tracker.waitForAll();
    }
    catch(java.lang.Exception e) {
      e.printStackTrace();
    }
    return img;
  }
  
  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new Runnable() {
      public void run() {
       JFrame frame = new ImageXOR();
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setSize(300, 300);
       frame.setVisible(true);
      }
    });
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
1) Use Graphics2D.drawImage(Image img, int x, int y, ImageObserver observer) instead.

or

2) Provide width/height arguments equal to the actual size of the image.

or

3) Do not use XOR mode.
Another testcase provided by Jan Bösenberg (INCORS GmbH)

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;

/**
* Class to reproduce a bug (?) with custom composites
*
* JRE 1.6 b72 throw as java.lang.InternalError: Cannot construct
general op for MaskBlit(...) Any CompositeContext
*/
public class CompositeBugTest {


 public static void main(String[] args) {
   JFrame frame = new JFrame("Composite Test");
   frame.setContentPane(new JPanelImage());
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   frame.setSize(200, 200);
   frame.validate();
   frame.setLocationRelativeTo(null);
   frame.setVisible(true);
 }

 private static class JPanelImage extends JPanel {
   private Image image = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);

   public JPanelImage() {
   }

   protected void paintComponent(Graphics g) {
     super.paintComponent(g);
     if (g instanceof Graphics2D) {
       Graphics2D g2D = (Graphics2D) g;
       g2D.setComposite(new TestComposite());
       // using drawImage(image, 0, 0, null) works without problems
       g2D.drawImage(image, 0, 0, 200, 200, null);
     } else {
       assert false;
     }
   }
 }


 private static class TestComposite implements Composite {

   public CompositeContext createContext(ColorModel srcColorModel,
ColorModel dstColorModel, RenderingHints hints) {
     return new TestCompositeContext();
   }

 }


 private static class TestCompositeContext implements CompositeContext {
   public void compose(Raster src1, Raster src2, WritableRaster dstOut) {
   }
   public void dispose() {
   }
 }
}