| Group: | Mathematical Functions |
| Topic: | Fourier and Wavelet transforms |
| See also: | invfwt2 fwt invfwt dwt invdwt fwtin fwtinshift |
| Function: | fwt2 | |
| Description: | The algorithm fwt2 is designed for 2 dimensional wavelet transformation. It mainly corresponds to dwt for the one dimensional case. If wished it works with the tensor product of one dimensional wavelet transforms. |
| Usage: | c = fwt2 (x, l, h, a) | |
| Input: | ||
| x | n x n matrix, the input data, where n has to be a power of 2 | |
| l | integer, l^2 is the number of the father wavelet coefficients | |
| h | m x 1 vector, wavelet basis | |
| a | integer, 0,1,2,3,... see notes | |
| Output: | ||
| c | n x n matrix, resulting coefficients | |
; load the wavelet library
library ("wavelet")
; initialize random generator
randomize(0)
; generate some data (line from top left to bottom right)
n = 16
i = 1:n
xo = (i.=i')
x = xo+0.2.*normal(n,n)
; compute bivariate wavelet coefficients
c = fwt2 (x, 4, daubechies4, 0);
; hard threshold
c = c.*(abs(c).>0.3)
; apply inverse transformation
y = invfwt2(c, 4, daubechies4, 0)
; compare orginal picture with thresholded picture
max(max(abs(y-xo),2))
Content of max [1,] 0.48421
| Group: | Mathematical Functions |
| Topic: | Fourier and Wavelet transforms |
| See also: | invfwt2 fwt invfwt dwt invdwt fwtin fwtinshift |