gcc/libjava/gnu/java/awt/BitwiseXORComposite.java

/* BitwiseXORComposite.java -- Composite for emulating old-style XOR.
   Copyright (C) 2003 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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independent module, the terms and conditions of the license of that
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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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exception statement from your version. */


package gnu.java.awt;

import java.awt.Color;
import java.awt.Composite;
import java.awt.CompositeContext;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;


/**
 * A composite for emulating traditional bitwise XOR of pixel values.
 * Please note that this composite does <i>not</i> implement the Porter-Duff
 * XOR operator, but an exclusive or of overlapping subpixel regions.
 *
 * <p><img src="doc-files/BitwiseXORComposite-1.png" width="545"
 * height="138" alt="A screen shot of BitwiseXORComposite in action"
 * />
 *
 * <p>The above screen shot shows the result of applying six different
 * BitwiseXORComposites. They were constructed with the colors colors
 * white, blue, black, orange, green, and brown, respectively. Each
 * composite was used to paint a fully white rectangle on top of the
 * blue bar in the background.
 * 
 * <p>The purpose of this composite is to support the {@link
 * Graphics#setXORMode(Color)} method in composite-aware graphics
 * implementations. Applications typically would use
 * <code>setXORMode</code> for drawing &#x201c;highlights&#x201d; such
 * as text selections or cursors by inverting colors temporarily and
 * then inverting them back.
 *
 * <p>A concrete <code>Graphics</code> implementation may contain
 * the following code:
 *
 * <p><pre> public void setXORMode(Color xorColor)
 * {
 *   setComposite(new gnu.java.awt.BitwiseXORComposite(xorColor));
 * }
 *
 * public void setPaintMode()
 * {
 *   setComposite(java.awt.AlphaComposite.SrcOver);
 * }</pre>
 *
 * @author Graydon Hoare (graydon@redhat.com)
 * @author Sascha Brawer (brawer@dandelis.ch)
 */
public class BitwiseXORComposite
  implements Composite
{
  /**
   * The color whose RGB value is xor-ed with the values of each
   * pixel.
   */
  protected Color xorColor;

  
  /**
   * Constructs a new composite for xor-ing the pixel value.
   *
   * @param xorColor the color whose pixel value will be bitwise
   * xor-ed with the source and destination pixels.
   */
  public BitwiseXORComposite(Color xorColor)
  {
    this.xorColor = xorColor;
  }


  /**
   * Creates a context object for performing the compositing
   * operation. Several contexts may co-exist for one composite; each
   * context may simultaneously be called from concurrent threads.
   *
   * @param srcColorModel the color model of the source.
   * @param dstColorModel the color model of the destination.
   * @param hints hints for choosing between rendering alternatives.
   */
  public CompositeContext createContext(ColorModel srcColorModel,
                                        ColorModel dstColorModel,
                                        RenderingHints hints)
  {
    if (IntContext.isSupported(srcColorModel, dstColorModel, hints))
      return new IntContext(srcColorModel, xorColor);

    return new GeneralContext(srcColorModel, dstColorModel, xorColor);
  }

  
  /**
   * A fallback CompositeContext that performs bitwise XOR of pixel
   * values with the pixel value of the specified <code>xorColor</code>.
   *
   * <p>Applying this CompositeContext on a 1024x1024 BufferedImage of
   * <code>TYPE_INT_RGB</code> took 611 ms on a lightly loaded 2.4 GHz
   * Intel Pentium 4 CPU running Sun J2SE 1.4.1_01 on GNU/Linux
   * 2.4.20. The timing is the average of ten runs on the same
   * BufferedImage. Since the measurements were taken with {@link
   * System#currentTimeMillis()}, they are rather inaccurate.
   *
   * @author Graydon Hoare (graydon@redhat.com)
   */
  private static class GeneralContext
    implements CompositeContext
  {
    ColorModel srcColorModel;
    ColorModel dstColorModel;
    Color xorColor;

    public GeneralContext(ColorModel srcColorModel,
                          ColorModel dstColorModel,
                          Color xorColor)
    {
      this.srcColorModel = srcColorModel;
      this.dstColorModel = dstColorModel;
      this.xorColor = xorColor;
    }


    public void compose(Raster src, Raster dstIn, WritableRaster dstOut)
    {
      Rectangle srcRect = src.getBounds();
      Rectangle dstInRect = dstIn.getBounds();
      Rectangle dstOutRect = dstOut.getBounds();
      
      int xp = xorColor.getRGB();
      int w = Math.min(Math.min(srcRect.width, dstOutRect.width),
                       dstInRect.width);
      int h = Math.min(Math.min(srcRect.height, dstOutRect.height),
                       dstInRect.height);

      Object srcPix = null, dstPix = null, rpPix = null;

      // Re-using the rpPix object saved 1-2% of execution time in
      // the 1024x1024 pixel benchmark.

      for (int y = 0; y < h; y++)
      {
        for (int x = 0; x < w; x++)
        {
          srcPix = src.getDataElements(x + srcRect.x, y + srcRect.y, srcPix);
          dstPix = dstIn.getDataElements(x + dstInRect.x, y + dstInRect.y,
                                         dstPix);
          int sp = srcColorModel.getRGB(srcPix);
          int dp = dstColorModel.getRGB(dstPix);
          int rp = sp ^ xp ^ dp;
          dstOut.setDataElements(x + dstOutRect.x, y + dstOutRect.y, 
                                 dstColorModel.getDataElements(rp, rpPix));
        }
      }
    }


    /**
     * Disposes any cached resources. The default implementation does
     * nothing because no resources are cached.
     */
    public void dispose()
    {
    }
  }


  /**
   * An optimized CompositeContext that performs bitwise XOR of
   * <code>int</code> pixel values with the pixel value of a specified
   * <code>xorColor</code>.  This CompositeContext working only for
   * rasters whose transfer format is {@link DataBuffer#TYPE_INT}.
   *
   * <p>Applying this CompositeContext on a 1024x1024 BufferedImage of
   * <code>TYPE_INT_RGB</code> took 69 ms on a lightly loaded 2.4 GHz
   * Intel Pentium 4 CPU running Sun J2SE 1.4.1_01 on GNU/Linux
   * 2.4.20. The timing is the average of ten runs on the same
   * BufferedImage. Since the measurements were taken with {@link
   * System#currentTimeMillis()}, they are rather inaccurate.
   *
   * @author Sascha Brawer (brawer@dandelis.ch)
   */
  private static class IntContext
    extends GeneralContext
  {
    public IntContext(ColorModel colorModel, Color xorColor)
    {
      super(colorModel, colorModel, xorColor);
    }


    public void compose(Raster src, Raster dstIn,
                        WritableRaster dstOut)
    {
      int aX, bX, dstX, aY, bY, dstY, width, height;
      int xorPixel;
      int[] srcLine, dstLine;

      aX = src.getMinX();
      aY = src.getMinY();
      bX = dstIn.getMinX();
      bY = dstIn.getMinY();
      dstX = dstOut.getMinX();
      dstY = dstOut.getMinY();
      width = Math.min(Math.min(src.getWidth(), dstIn.getWidth()),
                       dstOut.getWidth());
      height = Math.min(Math.min(src.getHeight(), dstIn.getHeight()),
                        dstOut.getHeight());
      if ((width < 1) || (height < 1))
        return;

      srcLine = new int[width];
      dstLine = new int[width];
      
      /* We need an int[] array with at least one element here;
       * srcLine is as good as any other.
       */
      srcColorModel.getDataElements(this.xorColor.getRGB(), srcLine);
      xorPixel = srcLine[0];

      for (int y = 0; y < height; y++)
      {
        src.getDataElements(aX, y + aY, width, 1, srcLine);
        dstIn.getDataElements(bX, y + bY, width, 1, dstLine);

        for (int x = 0; x < width; x++)
          dstLine[x] ^= srcLine[x] ^ xorPixel;

        dstOut.setDataElements(dstX, y + dstY, width, 1, dstLine);
      }
    }

    
    /**
     * Determines whether an instance of this CompositeContext would
     * be able to process the specified color models.
     */
    public static boolean isSupported(ColorModel srcColorModel,
                                      ColorModel dstColorModel,
                                      RenderingHints hints)
    {
      // FIXME: It would be good if someone could review these checks.
      // They probably need to be more restrictive.

      int transferType;

      transferType = srcColorModel.getTransferType();
      if (transferType != dstColorModel.getTransferType())
        return false;

      if (transferType != DataBuffer.TYPE_INT)
        return false;

      return true;
    }
  }
}