matlab中wavedec2,2-D wavelet decomposition

This example shows the structure of wavedec2 output matrices.

Load and display an image.

load woman

imagesc(X)

colormap(map)

Save the current discrete wavelet transform extension mode.

origMode = dwtmode(‘status’,’nodisplay’);

Change to periodic boundary handling. The dwtmode function displays a message indicating that the DWT extension mode is changing.

dwtmode(‘per’)

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! WARNING: Change DWT Extension Mode !

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

*****************************************

** DWT Extension Mode: Periodization **

*****************************************

Perform a level 3 decomposition of the image using the db1 (Haar) wavelet.

[c,s] = wavedec2(X,3,’db1′);

Return the number of elements in the image X and coefficient vector c. Confirm the number of elements in each are equal.

numel(X)

ans = 65536

numel(c)

ans = 65536

Display the bookkeeping matrix s. The first row displays the dimensions of the coarse scale approximation of the image. The last row displays the dimensions of the original image. The intermediate rows display the dimensions of the detail coefficients at the three levels of the decomposition, proceeding from coarse to fine scale.

s

s = 5×2

32 32

32 32

64 64

128 128

256 256

Reset discrete wavelet transform extension mode to its original mode.

dwtmode(origMode,’nodisplay’)