wpdec2 (Wavelet Toolbox)

Wavelet packet decomposition 2-D.

[T,D] = wpdec2(X,N,'wname',E,P)
[T,D] = wpdec2(X,N,'wname')

Description

wpdec2 is a two-dimensional wavelet packet analysis function.

[T,D] = wpdec2(X,N,'wname',E,P) returns a tree structure T and a data structure D (see maketree), corresponding to a wavelet packet decomposition of the matrix X, at level N, with a particular wavelet ('wname', see wfilters).

E is a string containing the type of entropy (see wentropy):

E = 'shannon', 'threshold', 'norm', 'log energy', 'sure', 'user'

P is an optional parameter:

'shannon' or 'log energy': P is not used

'threshold' or 'sure': P is the threshold (0

P)

'norm': P is a power (1

P < 2)

'user': P is a string containing a name of an user-defined function

[T,D] = wpdec2(X,N,'wname') is equivalent to
[T,D] = wpdec2(X,N,'wname','shannon').

See wpdec for a more complete description.

Examples

% Load image. 
    load tire 
    % X contains the loaded image.

% For an image the decomposition is performed using: 
    [t,d] = wpdec2(X,2,'db1'); 
    % default entropy is the shannon one.

% Plot tree structure (quarternary tree, or tree of order 4). 
    plottree(t)

Algorithm

The algorithm used for the wavelet packets decomposition follows the same line as the wavelet decomposition process (see dwt2, wavedec2).