Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Group: Mathematical Functions
Topic: Fourier and Wavelet transforms
See also: fwt2 fwt invfwt dwt invdwt fwtin invfwtin fwtinshift

Function: invfwt2
Description: The algorithm invfwt2 is designed for 2 dimensional inverse wavelet transformation. The wavelet coefficients are stored in the matrix c.

Link:
Usage: x = invfwt2 (c, l, h, a)
Input:
c n x n matrix, wavelet coefficients, retrieved e.g. by fwt2. n has to be a power of 2
l integer, l^2 is the number of the father wavelets coeffients
h m x 1 vector, wavelet basis
a integer, 0,1,2,3,... see notes
Output:
x n x n matrix,

Note:

Example:

; 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))

Result:



Contents of max

[1,]  0.48421 

Group: Mathematical Functions
Topic: Fourier and Wavelet transforms
See also: fwt2 fwt invfwt dwt invdwt fwtin invfwtin fwtinshift

Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

(C) MD*TECH Method and Data Technologies, 21.9.2000