This abstract class represents a subband in a bidirectional tree structure that describes the subband decomposition for a wavelet transform. This class is implemented by the SubbandAn and SubbandSyn classes, which are for the analysis and synthesis sides respectively.

       <p>The element can be either a node or a leaf of the tree. If it is a node,
       it has 4 descendants (LL, HL, LH and HH). If it is a leaf, it has no
       descendant.</p><p>The tree is bidirectional. Each element in the tree structure has a
       "parent", which is the subband from which the element was obtained by
       decomposition. The only exception is the root element which, for obvious
       reasons, has no parent (i.e. it is null).</p>

This interface defines the identifiers for the different types of filters that are supported.

       <p>The identifier values are the same as those used in the codestream
       syntax, for the filters that are defined in the standard.</p>

This interface defines how a wavelet filter implementation should present itself. This interface defines only the commonalities between the analysis and synthesis filters. The AnWTFilter and SynWTFilter classes provide the specifics of analysis and synthesis filters.

       <p>Both analysis and filters must be able to return the extent of the
       negative and positive support for both synthesis and analysis sides. This
       simplifies the sue of some functionalities that need extra information
       about the filters.</p>

This interface defines how a forward or inverse wavelet transform should present itself. As specified in the ImgData interface, from which this class inherits, all operations are confined to the current tile, and all coordinates are relative to it.

       <p>The definition of the methods in this interface allows for different
       types of implementation, reversibility and levels of decompositions for
       each component and each tile. An implementation of this interface does not
       need to support all this flexibility (e.g., it may provide the same
       implementation type and decomposition levels for all tiles and
       components).</p>