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javax.imageio.plugins.jpeg
Class JPEGHuffmanTable

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

public class JPEGHuffmanTable
extends Object

A class encapsulating a single JPEG Huffman table. Fields are provided for the "standard" tables from taken from Annex K of the JPEG specification. These are the tables used as defaults. This class differs from the old unsupported com.sun.image.codec.jpeg.JPEGHuffmanTable in two ways:

1. The lengths arrays for this class do not contain an ignored 0th entry. The lengths array in a JPEG stream does not contain an extra entry, and this class is used to represent the contents of a JPEG stream.
2. The old class incorrectly referred to Huffman "symbols", while expecting an array of values to be encoded. This class has a getValues method instead of a getSymbols method.

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 JPEGHuffmanTable	StdACChrominance The standard AC chrominance Huffman table.
static JPEGHuffmanTable	StdACLuminance The standard AC luminance Huffman table.
static JPEGHuffmanTable	StdDCChrominance The standard DC chrominance Huffman table.
static JPEGHuffmanTable	StdDCLuminance The standard DC luminance Huffman table.

Constructor Summary

JPEGHuffmanTable(short[] lengths, short[] values)
Creates a Huffman table and initializes it.

Method Summary

short[]	getLengths() Return an array of shorts containing the number of values for each length in the Huffman table.
short[]	getValues() Return an array of shorts containing the values arranged by increasing length of their corresponding codes.
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

StdDCLuminance

public static final JPEGHuffmanTable StdDCLuminance

The standard DC luminance Huffman table.

StdDCChrominance

public static final JPEGHuffmanTable StdDCChrominance

The standard DC chrominance Huffman table.

StdACLuminance

public static final JPEGHuffmanTable StdACLuminance

The standard AC luminance Huffman table.

StdACChrominance

public static final JPEGHuffmanTable StdACChrominance

The standard AC chrominance Huffman table.

Constructor Detail

JPEGHuffmanTable

public JPEGHuffmanTable(short[] lengths,
                        short[] values)

Creates a Huffman table and initializes it. The input arrays are copied. The arrays must describe a possible Huffman table. For example, 3 codes cannot be expressed with a single bit.

Parameters:

lengths - an array of shorts where lengths[k] is equal to the number of values with corresponding codes of length k + 1 bits.

values - an array of shorts containing the values in order of increasing code length.

Throws:

IllegalArgumentException - if lengths or values are null, the length of lengths is greater than 16, the length of values is greater than 256, if any value in lengths or values is less than zero, or if the arrays do not describe a valid Huffman table.

Method Detail

getLengths

public short[] getLengths()

Return an array of shorts containing the number of values for each length in the Huffman table. The returned array is a copy.

Returns:

a short array where array[k-1] is equal to the number of values in the table of length k.

See Also:

getValues()

getValues

public short[] getValues()

Return an array of shorts containing the values arranged by increasing length of their corresponding codes. The interpretation of the array is dependent on the values returned from getLengths. The returned array is a copy.

Returns:

a short array of values.

See Also:

getLengths()

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.