/* Kernel.java -- Java class for an image processing kernel
   Copyright (C) 2004, 2005, 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.

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permission to link this library with independent modules to produce an
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package java.awt.image;

/**
 * Kernel represents an image processing kernel.  It gets used to hold
 * convolution filters among other purposes.  It stores an array of float
 * values representing a 2-dimensional array in row-major order.
 *
 * @author Jerry Quinn (jlquinn@optonline.net)
 */
public class Kernel implements Cloneable
{
  /** The kernel width. */
  private final int width;
  
  /** The kernel height. */
  private final int height;
  
  /** Internal storage for the kernel's values. */
  private final float[] data;

  /**
   * Creates a new <code>Kernel</code> instance with the specified dimensions
   * and values.  The first <code>width * height</code> values in the specified
   * <code>data</code> array are copied to internal storage.
   *
   * @param width  the kernel width.
   * @param height  the kernel height.
   * @param data  the source data array (<code>null</code> not permitted).
   * 
   * @throws IllegalArgumentException if <code>data.length</code> is less than
   *     <code>width * height</code>.
   * @throws IllegalArgumentException if <code>width</code> or 
   *      <code>height</code> is less than zero.
   * @throws NullPointerException if <code>data</code> is <code>null</code>.
   */
  public Kernel(int width, int height, float[] data)
    throws IllegalArgumentException
  {
    this.width = width;
    this.height = height;
    if (data.length < width * height || width < 0 || height < 0)
      throw new IllegalArgumentException();
    this.data = new float[width * height];
    System.arraycopy(data, 0, this.data, 0, width * height);
  }

  /**
   * Returns the x-origin for the kernel, which is calculated as 
   * <code>(width - 1) / 2</code>.
   * 
   * @return The x-origin for the kernel.
   */
  public final int getXOrigin()
  {
    return (width - 1) / 2;
  }

  /**
   * Returns the y-origin for the kernel, which is calculated as
   * <code>(height - 1) / 2</code>.
   * 
   * @return The y-origin for the kernel.
   */
  public final int getYOrigin()
  {
    return (height - 1) / 2;
  }

  /**
   * Returns the kernel width (as supplied to the constructor).
   * 
   * @return The kernel width.
   */
  public final int getWidth()
  {
    return width;
  }

  /**
   * Returns the kernel height (as supplied to the constructor).
   * 
   * @return The kernel height.
   */
  public final int getHeight()
  {
    return height;
  }

  /**
   * Returns an array containing a copy of the kernel data.  If the 
   * <code>data</code> argument is non-<code>null</code>, the kernel values
   * are copied into it and then <code>data</code> is returned as the result.
   * If the <code>data</code> argument is <code>null</code>, this method 
   * allocates a new array then populates and returns it.
   *
   * @param data  an array to copy the return values into (if 
   *     <code>null</code>, a new array is allocated).
   *     
   * @return The array with copied values.
   * 
   * @throws IllegalArgumentException if <code>data.length</code> is less than 
   *     the kernel's <code>width * height</code>.
   */
  public final float[] getKernelData(float[] data)
    throws IllegalArgumentException
  {
    if (data == null)
      return (float[]) this.data.clone();

    if (data.length < this.data.length)
      throw new IllegalArgumentException();

    System.arraycopy(this.data, 0, data, 0, this.data.length);
    return data;
  }

  /**
   * Returns a clone of this kernel.
   * 
   * @return a clone of this Kernel.
   */
  public Object clone()
  {
    try
      {
        return super.clone();
      }
    catch (CloneNotSupportedException e)
      {
        throw (Error) new InternalError().initCause(e); // Impossible
      }
  }
}