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

Fields

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

Constructor Summary

Constructors

Constructor	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	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 declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Field Details

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 Details

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 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 Details

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.