/* LookupTable.java -- Java class for a pixel translation table.
   Copyright (C) 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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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);
}