/* BandCombineOp.java - perform a combination on the bands of a raster
   Copyright (C) 2004, 2006  Free Software Foundation

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.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

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
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
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
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */

package java.awt.image;

import java.awt.RenderingHints;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.Arrays;

/**
 * Filter Raster pixels by applying a matrix.
 *
 * BandCombineOp applies a matrix to each pixel to produce new pixel values.
 * The width of the matrix must be the same or one more than the number of
 * bands in the source Raster.  If one more, the pixels in the source are
 * assumed to contain an implicit 1.0 at the end.
 *
 * The rows of the matrix are multiplied by the pixel to produce the values
 * for the destination.  Therefore the destination Raster must contain the
 * same number of bands as the number of rows in the filter matrix.
 *
 * This Op assumes that samples are integers; floating point sample types will
 * be rounded to their nearest integer value during filtering.
 *
 * @author Jerry Quinn (jlquinn@optonline.net)
 */
public class BandCombineOp implements RasterOp
{
  private RenderingHints hints;
  private float[][] matrix;

  /**
   * Construct a BandCombineOp.
   *
   * @param matrix The matrix to filter pixels with.
   * @param hints Rendering hints to apply.  Ignored.
   * @throws ArrayIndexOutOfBoundsException if the matrix is invalid
   */
  public BandCombineOp(float[][] matrix, RenderingHints hints)
  {
    this.matrix = new float[matrix.length][];
    int width = matrix[0].length;
    for (int i = 0; i < matrix.length; i++)
      {
        this.matrix[i] = new float[width + 1];
        for (int j = 0; j < width; j++)
          this.matrix[i][j] = matrix[i][j];

        // The reference implementation pads the array with a trailing zero...
        this.matrix[i][width] = 0;
      }

    this.hints = hints;
  }

  /**
   * Filter Raster pixels through a matrix. Applies the Op matrix to source
   * pixes to produce dest pixels. Each row of the matrix is multiplied by the
   * src pixel components to produce the dest pixel. If matrix is one more than
   * the number of bands in the src, the last element is implicitly multiplied
   * by 1, i.e. added to the sum for that dest component. If dest is null, a
   * suitable Raster is created. This implementation uses
   * createCompatibleDestRaster.
   *
   * @param src The source Raster.
   * @param dest The destination Raster, or null.
   * @throws IllegalArgumentException if the destination raster is incompatible
   *           with the source raster.
   * @return The filtered Raster.
   * @see java.awt.image.RasterOp#filter(java.awt.image.Raster,
   *      java.awt.image.WritableRaster)
   */
  public WritableRaster filter(Raster src, WritableRaster dest) {
    if (dest == null)
      dest = createCompatibleDestRaster(src);
    else if (dest.getNumBands() != src.getNumBands()
             || dest.getTransferType() != src.getTransferType())
      throw new IllegalArgumentException("Destination raster is incompatible with source raster");

    // Filter the pixels
    int[] spix = new int[matrix[0].length - 1];
    int[] spix2 = new int[matrix[0].length - 1];
    int[] dpix = new int[matrix.length];
    for (int y = src.getMinY(); y < src.getHeight() + src.getMinY(); y++)
      for (int x = src.getMinX(); x < src.getWidth() + src.getMinX(); x++)
        {
          // In case matrix rows have implicit translation
          spix[spix.length - 1] = 1;
          src.getPixel(x, y, spix);

          // Do not re-calculate if pixel is identical to the last one
          // (ie, blocks of the same colour)
          if (!Arrays.equals(spix, spix2))
            {
              System.arraycopy(spix, 0, spix2, 0, spix.length);
              for (int i = 0; i < matrix.length; i++)
                {
                  dpix[i] = 0;
                  for (int j = 0; j < matrix[0].length - 1; j++)
                    dpix[i] += spix[j] * (int)matrix[i][j];
                }
            }
          dest.setPixel(x, y, dpix);
        }

    return dest;
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#getBounds2D(java.awt.image.Raster)
   */
  public final Rectangle2D getBounds2D(Raster src)
  {
    return src.getBounds();
  }

  /**
   * Creates a new WritableRaster that can be used as the destination for this
   * Op. The number of bands in the source raster must equal the number of rows
   * in the op matrix, which must also be equal to either the number of columns
   * or (columns - 1) in the matrix.
   *
   * @param src The source raster.
   * @return A compatible raster.
   * @see java.awt.image.RasterOp#createCompatibleDestRaster(java.awt.image.Raster)
   * @throws IllegalArgumentException if the raster is incompatible with the
   *           matrix.
   */
  public WritableRaster createCompatibleDestRaster(Raster src)
  {
    // Destination raster must have same number of bands as source
    if (src.getNumBands() != matrix.length)
      throw new IllegalArgumentException("Number of rows in matrix specifies an "
                                             + "incompatible number of bands");

    // We use -1 and -2 because we previously padded the rows with a trailing 0
    if (src.getNumBands() != matrix[0].length - 1
        && src.getNumBands() != matrix[0].length - 2)
      throw new IllegalArgumentException("Incompatible number of bands: "
                                             + "the number of bands in the raster must equal the number of "
                                             + "columns in the matrix, optionally minus one");

    return src.createCompatibleWritableRaster();
  }

  /**
   * Return corresponding destination point for source point.  Because this is
   * not a geometric operation, it simply returns a copy of the source.
   *
   * @param src The source point.
   * @param dst The destination point.
   * @return dst The destination point.
   * @see java.awt.image.RasterOp#getPoint2D(java.awt.geom.Point2D,
   *java.awt.geom.Point2D)
   */
  public final Point2D getPoint2D(Point2D src, Point2D dst)
  {
    if (dst == null)
      return (Point2D)src.clone();

    dst.setLocation(src);
    return dst;
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#getRenderingHints()
   */
  public final RenderingHints getRenderingHints()
  {
    return hints;
  }

  /**
   * Return the matrix used in this operation.
   *
   * @return The matrix used in this operation.
   */
  public final float[][] getMatrix()
  {
    return matrix;
  }

}