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/* LookupTable.java -- Java class for a pixel translation table.

   Copyright (C) 2004, 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

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;

/**

 * LookupTable represents translation arrays for pixel values.  It wraps one

 * or more data arrays for each layer (or component) in an image, such as

 * Alpha, R, G, and B.  When doing translation, the offset is subtracted from

 * the pixel values to allow a subset of an array to be used.

 *

 * @see ByteLookupTable

 * @see ShortLookupTable

 *

 * @author Jerry Quinn (jlquinn@optonline.net)

 * @version 1.0

 */

public abstract class LookupTable

{

  // Not protected since that's part of the public API.

  int offset;

  int numComponents;

  /**

   * Creates a new <code>LookupTable</code> instance.

   *

   * If numComponents is 1, the same translation table is used for all pixel

   * components.

   *

   * @param offset Offset to be subtracted.

   * @param numComponents Number of image components.

   * @exception IllegalArgumentException if offset < 0 or numComponents < 1.

   */

  protected LookupTable(int offset, int numComponents)

    throws IllegalArgumentException

  {

    if (offset < 0 || numComponents < 1)

      throw new IllegalArgumentException();

    this.offset = offset;

    this.numComponents = numComponents;

  }

  /** Return the number of components. */

  public int getNumComponents()

  {

    return numComponents;

  }

  /** Return the offset. */

  public int getOffset()

  {

    return offset;

  }

  /**

   * Return translated values for a pixel.

   *

   * For each value in the pixel src, use the value minus offset as an index

   * in the component array and copy the value there to the output for the

   * component.  If dest is null, the output is a new array, otherwise the

   * translated values are written to dest.  Dest can be the same array as

   * src.

   *

   * For example, if the pixel src is [2, 4, 3], and offset is 1, the output

   * is [comp1[1], comp2[3], comp3[2]], where comp1, comp2, and comp3 are the

   * translation arrays.

   *

   * @param src Component values of a pixel.

   * @param dest Destination array for values, or null.

   * @return Translated values for the pixel.

   */

  public abstract int[] lookupPixel(int[] src, int[] dest);

}