001/* LookupTable.java -- Java class for a pixel translation table.
002   Copyright (C) 2004, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.awt.image;
040
041/**
042 * LookupTable represents translation arrays for pixel values.  It wraps one
043 * or more data arrays for each layer (or component) in an image, such as
044 * Alpha, R, G, and B.  When doing translation, the offset is subtracted from
045 * the pixel values to allow a subset of an array to be used.
046 *
047 * @see ByteLookupTable
048 * @see ShortLookupTable
049 *
050 * @author Jerry Quinn (jlquinn@optonline.net)
051 * @version 1.0
052 */
053public abstract class LookupTable
054{
055  // Not protected since that's part of the public API.
056  int offset;
057  int numComponents;
058
059  /**
060   * Creates a new <code>LookupTable</code> instance.
061   *
062   * If numComponents is 1, the same translation table is used for all pixel
063   * components.
064   * 
065   * @param offset Offset to be subtracted.
066   * @param numComponents Number of image components.
067   * @exception IllegalArgumentException if offset < 0 or numComponents < 1.
068   */
069  protected LookupTable(int offset, int numComponents)
070    throws IllegalArgumentException
071  {
072    if (offset < 0 || numComponents < 1)
073      throw new IllegalArgumentException();
074    this.offset = offset;
075    this.numComponents = numComponents;
076  }
077
078  /** Return the number of components. */
079  public int getNumComponents()
080  {
081    return numComponents;
082  }
083
084  /** Return the offset. */
085  public int getOffset()
086  {
087    return offset;
088  }
089
090  
091  /**
092   * Return translated values for a pixel.
093   *
094   * For each value in the pixel src, use the value minus offset as an index
095   * in the component array and copy the value there to the output for the
096   * component.  If dest is null, the output is a new array, otherwise the
097   * translated values are written to dest.  Dest can be the same array as
098   * src.
099   *
100   * For example, if the pixel src is [2, 4, 3], and offset is 1, the output
101   * is [comp1[1], comp2[3], comp3[2]], where comp1, comp2, and comp3 are the
102   * translation arrays.
103   *
104   * @param src Component values of a pixel.
105   * @param dest Destination array for values, or null.
106   * @return Translated values for the pixel.
107   */
108  public abstract int[] lookupPixel(int[] src, int[] dest);
109}