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/* JPEGQTable.java --

 Copyright (C)  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

 the Free Software Foundation; either version 2, or (at your option)

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 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

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 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

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 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

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 independent module, the terms and conditions of the license of that

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package javax.imageio.plugins.jpeg;

import gnu.java.lang.CPStringBuilder;

/**

 * The JPEGQTable class represents a quantization table that can be

 * used to encode or decode a JPEG stream.  The standard JPEG

 * luminance and chrominance quantization tables are provided as

 * static fields.  Table entries are stored in natural order, not

 * zig-zag order.

 */

public class JPEGQTable

{

  /**

   * The table entries, stored in natural order.

   */

  private int[] table;

  /**

   * The standard JPEG luminance quantization table.  Values are

   * stored in natural order.

   */

  public static final JPEGQTable K1Luminance = new JPEGQTable(new int[]

      {

        16, 11, 10, 16,  24,  40,  51,  61,

        12, 12, 14, 19,  26,  58,  60,  55,

        14, 13, 16, 24,  40,  57,  69,  56,

        14, 17, 22, 29,  51,  87,  80,  62,

        18, 22, 37, 56,  68, 109, 103,  77,

        24, 35, 55, 64,  81, 104, 113,  92,

        49, 64, 78, 87, 103, 121, 120, 101,

        72, 92, 95, 98, 112, 100, 103,  99

      }, false);

  /**

   * The standard JPEG luminance quantization table, scaled by

   * one-half.  Values are stored in natural order.

   */

  public static final JPEGQTable K1Div2Luminance =

    K1Luminance.getScaledInstance(0.5f, true);

  /**

   * The standard JPEG chrominance quantization table.  Values are

   * stored in natural order.

   */

  public static final JPEGQTable K2Chrominance = new JPEGQTable(new int[]

      {

        17, 18, 24, 47, 99, 99, 99, 99,

        18, 21, 26, 66, 99, 99, 99, 99,

        24, 26, 56, 99, 99, 99, 99, 99,

        47, 66, 99, 99, 99, 99, 99, 99,

        99, 99, 99, 99, 99, 99, 99, 99,

        99, 99, 99, 99, 99, 99, 99, 99,

        99, 99, 99, 99, 99, 99, 99, 99,

        99, 99, 99, 99, 99, 99, 99, 99

      }, false);

  /**

   * The standard JPEG chrominance quantization table, scaled by

   * one-half.  Values are stored in natural order.

   */

  public static final JPEGQTable K2Div2Chrominance =

    K2Chrominance.getScaledInstance(0.5f, true);

  /**

   * Construct a new JPEG quantization table.  A copy is created of

   * the table argument.

   *

   * @param table the 64-element value table, stored in natural order

   *

   * @throws IllegalArgumentException if the table is null or if

   * table's length is not equal to 64.

   */

  public JPEGQTable(int[] table)

  {

    this(checkTable(table), true);

  }

  /**

   * Private constructor that avoids unnecessary copying and argument

   * checking.

   *

   * @param table the 64-element value table, stored in natural order

   * @param copy true if a copy should be created of the given table

   */

  private JPEGQTable(int[] table, boolean copy)

  {

    this.table = copy ? (int[]) table.clone() : table;

  }

  private static int[] checkTable(int[] table)

  {

    if (table == null || table.length != 64)

      throw new IllegalArgumentException("invalid JPEG quantization table");

    return table;

  }

  /**

   * Retrieve a copy of the quantization values for this table.

   *

   * @return a copy of the quantization value array

   */

  public int[] getTable()

  {

    return (int[]) table.clone();

  }

  /**

   * Retrieve a copy of this JPEG quantization table with every value

   * scaled by the given scale factor, and clamped from 1 to 255

   * baseline or from 1 to 32767 otherwise.

   *

   * @param scaleFactor the factor by which to scale this table

   * @param forceBaseline clamp scaled values to a maximum of 255 if

   * true, 32767 if false

   *

   * @return a new scaled JPEG quantization table

   */

  public JPEGQTable getScaledInstance(float scaleFactor,

                                      boolean forceBaseline)

  {

    int[] scaledTable = getTable();

    int max = forceBaseline ? 255 : 32767;

    for (int i = 0; i < scaledTable.length; i++)

      {

        scaledTable[i] = Math.round (scaleFactor * (float) scaledTable[i]);

        if (scaledTable[i] < 1)

          scaledTable[i] = 1;

        else if (scaledTable[i] > max)

          scaledTable[i] = max;

      }

    // Do not copy scaledTable.  It is already a copy because we used

    // getTable to retrieve it.

    return new JPEGQTable(scaledTable, false);

  }

  /**

   * Create a string representing this JPEG quantization table.

   */

  public String toString()

  {

    CPStringBuilder buffer = new CPStringBuilder();

    buffer.append("JPEGQTable:\n");

    for (int i = 0; i < 8; i++)

      {

        buffer.append("        ");

        for (int j = 0; j < 8; j++)

          {

            buffer.append(table[i * 8 + j] + " ");

          }

        buffer.append("\n");

      }

    return buffer.toString();

  }

}