/* JPEGQTable.java --
Copyright (C) 2006 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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package javax.imageio.plugins.jpeg;
/**
* 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()
{
StringBuffer buffer = new StringBuffer();
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();
}
}