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 spec, as well as the default tables conventionally used for visually lossless encoding.

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

 

Field Summary

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.2, with all elements divided by 2.
 

 

Constructor Summary

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

 

Method Summary

 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 representation of the object.
 
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.2, 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 scaleFactorless 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 - the multiplicative 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()
Description copied from class: Object
Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of: 

 getClass().getName() + '@' + Integer.toHexString(hashCode())

Overrides:
toString in class Object
Returns:
a string representation of the object.