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javax.imageio.plugins.jpeg
Class JPEGQTable

java.lang.Object
  javax.imageio.plugins.jpeg.JPEGQTable

public class JPEGQTable
extends Object

A class encapsulating a single JPEG quantization table. The elements appear in natural order (as opposed to zig-zag order). Static variables are provided for the "standard" tables taken from Annex K of the JPEG specification, as well as the default tables conventionally used for visually lossless encoding.

For more information about the operation of the standard JPEG plug-in, see the JPEG metadata format specification and usage notes

Field Summary

Modifier and Type	Field and Description
static JPEGQTable	K1Div2Luminance The sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.
static JPEGQTable	K1Luminance The sample luminance quantization table given in the JPEG specification, table K.1.
static JPEGQTable	K2Chrominance The sample chrominance quantization table given in the JPEG specification, table K.2.
static JPEGQTable	K2Div2Chrominance The sample chrominance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.

Constructor and Description

JPEGQTable(int[] table)
Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order).

Method Summary

Modifier and Type	Method and Description
JPEGQTable	getScaledInstance(float scaleFactor, boolean forceBaseline) Returns a new quantization table where the values are multiplied by scaleFactor and then clamped to the range 1..32767 (or to 1..255 if forceBaseline is true).
int[]	getTable() Returns a copy of the current quantization table as an array of ints in natural (not zig-zag) order.
String	toString() Returns a String representing this quantization table.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

K1Luminance

public static final JPEGQTable K1Luminance

The sample luminance quantization table given in the JPEG specification, table K.1. According to the specification, these values produce "good" quality output.

See Also:

K1Div2Luminance

K1Div2Luminance

public static final JPEGQTable K1Div2Luminance

The sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2. According to the specification, these values produce "very good" quality output. This is the table usually used for "visually lossless" encoding, and is the default luminance table used if the default tables and quality settings are used.

See Also:

K1Luminance

K2Chrominance

public static final JPEGQTable K2Chrominance

The sample chrominance quantization table given in the JPEG specification, table K.2. According to the specification, these values produce "good" quality output.

See Also:

K2Div2Chrominance

K2Div2Chrominance

public static final JPEGQTable K2Div2Chrominance

The sample chrominance quantization table given in the JPEG specification, table K.1, with all elements divided by 2. According to the specification, these values produce "very good" quality output. This is the table usually used for "visually lossless" encoding, and is the default chrominance table used if the default tables and quality settings are used.

See Also:

K2Chrominance

Constructor Detail

JPEGQTable

public JPEGQTable(int[] table)

Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order). A copy is made of the the input array.

Parameters:

table - the quantization table, as an int array.

Throws:

IllegalArgumentException - if table is null or table.length is not equal to 64.

Method Detail

getTable

public int[] getTable()

Returns a copy of the current quantization table as an array of ints in natural (not zig-zag) order.

Returns:

A copy of the current quantization table.

getScaledInstance

public JPEGQTable getScaledInstance(float scaleFactor,
                                    boolean forceBaseline)

Returns a new quantization table where the values are multiplied by scaleFactor and then clamped to the range 1..32767 (or to 1..255 if forceBaseline is true).

Values of scaleFactor less than 1 tend to improve the quality level of the table, and values greater than 1.0 degrade the quality level of the table.

Parameters:

scaleFactor - multiplication factor for the table.

forceBaseline - if true, the values will be clamped to the range 1..255

Returns:

a new quantization table that is a linear multiple of the current table.

toString

public String toString()

Returns a String representing this quantization table.

Overrides:

toString in class Object

Returns:

a String representing this quantization table.