jj2000.j2k.codestream.reader

Class TagTreeDecoder

java.lang.Object

jj2000.j2k.codestream.reader.TagTreeDecoder

public class TagTreeDecoder
extends Object

This class implements the tag tree decoder. A tag tree codes a 2D matrix of integer elements in an efficient way. The decoding procedure 'update()' updates a value of the matrix from a stream of coded data, given a threshold. This procedure decodes enough information to identify whether or not the value is greater than or equal to the threshold, and updates the value accordingly.

In general the decoding procedure must follow the same sequence of elements and thresholds as the encoding one. The encoder is implemented by the TagTreeEncoder class.

Tag trees that have one dimension, or both, as 0 are allowed for convenience. Of course no values can be set or coded in such cases.

See Also:

TagTreeEncoder

Field Summary

Fields

Modifier and Type	Field and Description
protected int	h The vertical dimensions of the base level
protected int	lvls The number of levels in the tag tree
protected int[][]	treeS The tag tree state.
protected int[][]	treeV The tag tree values.
protected int	w The horizontal dimension of the base level

Constructor Summary

Constructors

Constructor and Description
TagTreeDecoder(int h, int w) Creates a tag tree decoder with 'w' elements along the horizontal dimension and 'h' elements along the vertical direction.

Method Summary

Modifier and Type	Method and Description
int	getHeight() Returns the number of leafs along the vertical direction.
int	getValue(int m, int n) Returns the current value of the specified element in the tag tree.
int	getWidth() Returns the number of leafs along the horizontal direction.
int	update(int m, int n, int t, jj2000.j2k.codestream.reader.PktHeaderBitReader in) Decodes information for the specified element of the tree, given the threshold, and updates its value.

Methods inherited from class java.lang.Object

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

Field Detail

w

protected int w

The horizontal dimension of the base level

h

protected int h

The vertical dimensions of the base level

lvls

protected int lvls

The number of levels in the tag tree

treeV

protected int[][] treeV

The tag tree values. The first index is the level, starting at level 0 (leafs). The second index is the element within the level, in lexicographical order.

treeS

protected int[][] treeS

The tag tree state. The first index is the level, starting at level 0 (leafs). The second index is the element within the level, in lexicographical order.

Constructor Detail

TagTreeDecoder

public TagTreeDecoder(int h,
                      int w)

Creates a tag tree decoder with 'w' elements along the horizontal dimension and 'h' elements along the vertical direction. The total number of elements is thus 'vdim' x 'hdim'.

The values of all elements are initialized to Integer.MAX_VALUE (i.e. no information decoded so far). The states are initialized all to 0.

Parameters:

h - The number of elements along the vertical direction.

w - The number of elements along the horizontal direction.

Method Detail

getWidth

public final int getWidth()

Returns the number of leafs along the horizontal direction.

Returns:

The number of leafs along the horizontal direction.

getHeight

public final int getHeight()

Returns the number of leafs along the vertical direction.

Returns:

The number of leafs along the vertical direction.

update

public int update(int m,
                  int n,
                  int t,
                  jj2000.j2k.codestream.reader.PktHeaderBitReader in)
           throws IOException

Decodes information for the specified element of the tree, given the threshold, and updates its value. The information that can be decoded is whether or not the value of the element is greater than, or equal to, the value of the threshold.

Parameters:

m - The vertical index of the element.

n - The horizontal index of the element.

t - The threshold to use in decoding. It must be non-negative.

in - The stream from where to read the coded information.

Returns:

The updated value at position (m,n).

Throws:

IOException - If an I/O error occurs while reading from 'in'.

EOFException - If the ned of the 'in' stream is reached before getting all the necessary data.

getValue

public int getValue(int m,
                    int n)

Returns the current value of the specified element in the tag tree. This is the value as last updated by the update() method.

Parameters:

m - The vertical index of the element.

n - The horizontal index of the element.

Returns:

The current value of the element.

See Also:

update(int, int, int, jj2000.j2k.codestream.reader.PktHeaderBitReader)