/* AreaAveragingScaleFilter.java -- Java class for filtering images
   Copyright (C) 1999,2006 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
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02110-1301 USA.

Linking this library statically or dynamically with other modules is
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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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terms of your choice, provided that you also meet, for each linked
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package java.awt.image;

/**
 * This filter should produce images which do not have image artifacts
 * like broken lines which were originally unbroken.  The cost is of
 * course speed.  Using bi-linear interpolation here against 4 pixel
 * points should give the desired results although Sun does not 
 * specify what the exact algorithm should be.
 * <br>
 *
 * @author C. Brian Jones (cbj@gnu.org) 
 */
public class AreaAveragingScaleFilter extends ReplicateScaleFilter
{
  /**
   * Construct an instance of <code>AreaAveragingScaleFilter</code> which
   * should be used in conjunction with a <code>FilteredImageSource</code>
   * object.
   * 
   * @param width the width of the destination image
   * @param height the height of the destination image
   */
  public AreaAveragingScaleFilter(int width, int height) {
    super(width, height);
  }

  /**
   * The <code>ImageProducer</code> should call this method with a
   * bit mask of hints from any of <code>RANDOMPIXELORDER</code>,
   * <code>TOPDOWNLEFTRIGHT</code>, <code>COMPLETESCANLINES</code>,
   * <code>SINGLEPASS</code>, <code>SINGLEFRAME</code> from the 
   * <code>ImageConsumer</code> interface.
   * <br>
   * FIXME - more than likely Sun's implementation desires 
   * <code>TOPDOWNLEFTRIGHT</code> order and this method is overloaded here
   * in order to assure that mask is part of the hints added to
   * the consumer.
   * 
   * @param flags a bit mask of hints
   * @see ImageConsumer
   */
  public void setHints(int flags)
  {
    if (consumer != null)
      consumer.setHints(flags);
  }

  /**
   * This function delivers a rectangle of pixels where any
   * pixel(m,n) is stored in the array as a <code>byte</code> at
   * index (n * scansize + m + offset).  
   *
   * @param x the x coordinate of the rectangle
   * @param y the y coordinate of the rectangle
   * @param w the width of the rectangle
   * @param h the height of the rectangle
   * @param model the <code>ColorModel</code> used to translate the pixels
   * @param pixels the array of pixel values
   * @param offset the index of the first pixels in the <code>pixels</code> array
   * @param scansize the width to use in extracting pixels from the <code>pixels</code> array
   */
  public void setPixels(int x, int y, int w, int h, 
			ColorModel model, byte[] pixels, int offset, int scansize)
  {
    double rx = ((double) srcWidth) / destWidth;
    double ry = ((double) srcHeight) / destHeight;

    int destScansize = (int) Math.round(scansize / rx);

    byte[] destPixels = averagePixels(x, y, w, h,
				      model, pixels, offset, scansize,
				      rx, ry, destScansize);

    if (consumer != null)
      consumer.setPixels((int) Math.floor(x/rx), (int) Math.floor(y/ry),
			 (int) Math.ceil(w/rx), (int) Math.ceil(h/ry),
			 model, destPixels, 0, destScansize);
  }

  /**
   * This function delivers a rectangle of pixels where any
   * pixel(m,n) is stored in the array as an <code>int</code> at
   * index (n * scansize + m + offset).  
   *
   * @param x the x coordinate of the rectangle
   * @param y the y coordinate of the rectangle
   * @param w the width of the rectangle
   * @param h the height of the rectangle
   * @param model the <code>ColorModel</code> used to translate the pixels
   * @param pixels the array of pixel values
   * @param offset the index of the first pixels in the <code>pixels</code> array
   * @param scansize the width to use in extracting pixels from the <code>pixels</code> array
   */
  public void setPixels(int x, int y, int w, int h, 
			ColorModel model, int[] pixels, int offset, int scansize)
  {
    double rx = ((double) srcWidth) / destWidth;
    double ry = ((double) srcHeight) / destHeight;

    int destScansize = (int) Math.round(scansize / rx);

    int[] destPixels = averagePixels(x, y, w, h,
				     model, pixels, offset, scansize,
				     rx, ry, destScansize);

    if (consumer != null)
      consumer.setPixels((int) Math.floor(x/rx), (int) Math.floor(y/ry),
			 (int) Math.ceil(w/rx), (int) Math.ceil(h/ry),
			 model, destPixels, 0, destScansize);
  }

  /**
   * This is a really terrible implementation, 
   * since it uses the nearest-neighbor method. This filter is rarely used though.
   *
   * @param srcx, srcy - Source rectangle upper-left corner
   * @param srcw, srch - Source rectangle width and height
   * @param model - Pixel color model
   * @param srcPixels - Source pixel data.
   * @param srcOffset - Starting offset into the source pixel data array.
   * @param srcScansize - Source array scanline size.
   * @param rx,ry - Scaling factor.
   * @param dstScansize - Destination array scanline size.
   */
  private byte[] averagePixels(int srcx, int srcy, int srcw, int srch,
			       ColorModel model, byte[] srcPixels,
			       int srcOffset, int srcScansize,
			       double rx, double ry, int destScansize)
  {
    int destW = (int) Math.ceil(srcw/rx);
    int destH = (int) Math.ceil(srch/ry);
    byte[] destPixels = new byte[ destW * destH ];
    int sx, sy;

    int w = (int)Math.ceil(rx);
    int h = (int)Math.ceil(ry);

    for(int x = 0; x < destW; x++)
      for(int y = 0; y < destH; y++)
	{
	  sx = (int) (x * rx);
	  sy = (int) (y * ry);

	  int r,g,b,a;
	  r = g = b = a = 0;

	  for(int i = 0; i < w; i++)
	    {
	      for(int j = 0; j < h; j++)
		{
		  int idx = srcx + sx + i + (srcy + sy + j)*srcScansize;
		  r += model.getRed(srcPixels[ idx ]);
		  g += model.getGreen(srcPixels[ idx ]);
		  b += model.getBlue(srcPixels[ idx ]);
		  a += model.getAlpha(srcPixels[ idx ]);
		}
	    }
	    
	  r = r / (w * h);
	  g = g / (w * h);
	  b = b / (w * h);
	  a = a / (w * h);

	  // Does this really work?
	  destPixels[x + destScansize*y] = (byte)model.getDataElement
	    (new int[]{r, g, b, a}, 0);
	}

    return destPixels;
  }

  /**
   * This is a really terrible implementation, 
   * since it uses the nearest-neighbor method. This filter is rarely used though.
   *
   * @param srcx, srcy - Source rectangle upper-left corner
   * @param srcw, srch - Source rectangle width and height
   * @param model - Pixel color model
   * @param srcPixels - Source pixel data.
   * @param srcOffset - Starting offset into the source pixel data array.
   * @param srcScansize - Source array scanline size.
   * @param rx,ry - Scaling factor.
   * @param dstScansize - Destination array scanline size.
   */
  private int[] averagePixels(int srcx, int srcy, int srcw, int srch,
			      ColorModel model, int[] srcPixels,
			      int srcOffset, int srcScansize,
			      double rx, double ry, int destScansize)
  {
    int destW = (int) Math.ceil(srcw/rx);
    int destH = (int) Math.ceil(srch/ry);
    int[] destPixels = new int[ destW * destH ];
    int sx, sy;
    
    int w = (int)Math.ceil(rx);
    int h = (int)Math.ceil(ry);
    
    for(int x = 0; x < destW; x++)
      for(int y = 0; y < destH; y++)
	{
	  sx = (int) (x * rx);
	  sy = (int) (y * ry);
	  
	  int r,g,b,a;
	  r = g = b = a = 0;
	  
	  for(int i = 0; i < w; i++)
	    {
	      for(int j = 0; j < h; j++)
		{
		  int idx = srcx + sx + i + (srcy + sy + j)*srcScansize;
		  r += model.getRed(srcPixels[ idx ]);
		  g += model.getGreen(srcPixels[ idx ]);
		  b += model.getBlue(srcPixels[ idx ]);
		  a += model.getAlpha(srcPixels[ idx ]);
		}
	    }
	  
	  r = r / (w * h);
	  g = g / (w * h);
	  b = b / (w * h);
	  a = a / (w * h);

	  destPixels[x + destScansize*y] = model.getDataElement
	    (new int[]{r, g, b, a}, 0);
	}
    
    return destPixels;
  }
}