/* RGBImageFilter.java -- Java class for filtering Pixels by RGB values
   Copyright (C) 1999, 2005  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.

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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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package java.awt.image;

/**
 * A filter designed to filter images in the default RGBColorModel regardless of 
 * the ImageProducer's ColorModel.
 *
 * @author Mark Benvenuto (mcb54@columbia.edu)
 */
public abstract class RGBImageFilter extends ImageFilter
{
  protected ColorModel origmodel;

  protected ColorModel newmodel;
    
  /**
   * Specifies whether to apply the filter to the index entries of the
   * IndexColorModel. Subclasses should set this to true if the filter
   * does not depend on the pixel's coordinate.
   */
  protected boolean canFilterIndexColorModel = false;

  /**
   * Construct new RGBImageFilter.
   */
  public RGBImageFilter() 
  {
  }

  /**
   * Sets the ColorModel used to filter with. If the specified ColorModel is
   * IndexColorModel and canFilterIndexColorModel is true, we subsitute the
   * ColorModel for a filtered one here and in setPixels whenever the original
   * one appears. Otherwise overrides the default ColorModel of ImageProducer
   * and specifies the default RGBColorModel
   *
   * @param model the color model to be used most often by setPixels
   *
   * @see ColorModel
   */
  public void setColorModel(ColorModel model) 
  {
    if ((model instanceof IndexColorModel) && canFilterIndexColorModel)
      {
        ColorModel newCM = filterIndexColorModel((IndexColorModel) model);
        substituteColorModel(model, newCM);
        consumer.setColorModel(newmodel);
      }
    else
      {
        consumer.setColorModel(ColorModel.getRGBdefault());
      }
  }

  /**
   * Registers a new ColorModel to subsitute for the old ColorModel when 
   * setPixels encounters the a pixel with the old ColorModel. The pixel 
   * remains unchanged except for a new ColorModel.
   * 
   * @param oldcm the old ColorModel
   * @param newcm the new ColorModel
   */
  public void substituteColorModel(ColorModel oldcm, ColorModel newcm)
  {
    origmodel = oldcm;
    newmodel = newcm;
  }

  /**
   * Filters an IndexColorModel through the filterRGB function. Uses
   * coordinates of -1 to indicate its filtering an index and not a pixel.
   *
   * @param icm an IndexColorModel to filter
   */
  public IndexColorModel filterIndexColorModel(IndexColorModel icm) 
  {
    int len = icm.getMapSize();
    byte[] reds = new byte[len];
    byte[] greens = new byte[len];
    byte[] blues = new byte[len];
    byte[] alphas = new byte[len];

    icm.getAlphas( alphas );
    icm.getReds( reds );
    icm.getGreens( greens );
    icm.getBlues( blues );

    int transparent = icm.getTransparentPixel();
    boolean needAlpha = false;
    for( int i = 0; i < len; i++ )
      {
        int rgb = filterRGB(-1, -1, icm.getRGB(i));
        alphas[i] = (byte) (rgb >> 24);
        if (alphas[i] != ((byte) 0xff) && i != transparent)
          needAlpha = true;
        reds[i] = (byte) (rgb >> 16);
        greens[i] = (byte) (rgb >> 8);
        blues[i] = (byte) (rgb);
      }
    IndexColorModel newIcm;
    if (needAlpha)
      newIcm = new IndexColorModel(icm.getPixelSize(), len, reds, greens,
                                   blues, alphas);
    else
      newIcm = new IndexColorModel(icm.getPixelSize(), len, reds, greens,
                                   blues, transparent);
    return newIcm;
  }

  /**
   * This functions filters a set of RGB pixels through filterRGB.
   *
   * @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 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 filterRGBPixels(int x, int y, int w, int h, int[] pixels,
                              int offset, int scansize)
  {
    int index = offset;
    for (int yp = 0; yp < h; yp++)
      {
        for (int xp = 0; xp < w; xp++)
          {
            pixels[index] = filterRGB(xp + x, yp + y, pixels[index]);
            index++;
          }
        index += scansize - w;
      }
    consumer.setPixels(x, y, w, h, ColorModel.getRGBdefault(), pixels, offset,
                       scansize);
  }

  /**
   * If the ColorModel is the same ColorModel which as already converted 
   * then it converts it the converted ColorModel. Otherwise it passes the 
   * array of pixels through filterRGBpixels.
   *
   * @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)
  {
    if (model == origmodel)
      {
        consumer.setPixels(x, y, w, h, newmodel, pixels, offset, scansize);
      }
    else
      {
        int[] filtered = new int[w];
        int index = offset;
        for (int yp = 0; yp < h; yp++)
          {
            for (int xp = 0; xp < w; xp++)
              {
                filtered[xp] = model.getRGB((pixels[index] & 0xff));
                index++;
              }
            index += scansize - w;
            filterRGBPixels(x, y + yp, w, 1, filtered, 0, w);
          }
      }
  }

  /**
   * 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)
  {
    if (model == origmodel)
      {
        consumer.setPixels(x, y, w, h, newmodel, pixels, offset, scansize);
      }
    else
      {
        int[] filtered = new int[w];
        int index = offset;
        for (int yp = 0; yp < h; yp++)
          {
            for (int xp = 0; xp < w; xp++)
              {
                filtered[xp] = model.getRGB((pixels[index]));
                index++;
              }
            index += scansize - w;
            filterRGBPixels(x, y + yp, w, 1, filtered, 0, w);
          }
      }
  }

  /**
   * Filters a single pixel from the default ColorModel.
   *
   * @param x x-coordinate
   * @param y y-coordinate
   * @param rgb color
   */
  public abstract int filterRGB(int x, int y, int rgb);
}
