IFWT Inverse Fast Wavelet Transform
Usage: f = ifwt(c,info)
f = ifwt(c,w,J,Ls)
f = ifwt(c,w,J,Ls,dim)
Input parameters:
c : Wavelet coefficients.
info,w : Transform parameters struct/Wavelet filters definition.
J : Number of filterbank iterations.
Ls : Length of the reconstructed signal.
dim : Dimension to along which to apply the transform.
Output parameters:
f : Reconstructed data.
f = IFWT(c,info) reconstructs signal f from the wavelet coefficients
c using parameters from info struct. both returned by FWT
function.
f = IFWT(c,w,J,Ls) reconstructs signal f from the wavelet coefficients
c using J*-iteration synthesis filterbank build from the basic
filterbank defined by w. The Ls parameter is mandatory due to the
ambiguity of lengths introduced by the subsampling operation and by
boundary treatment methods. Note that the same flag as in the FWT
function have to be used, otherwise perfect reconstruction cannot be
obtained.
In both cases, the fast wavelet transform algorithm (Mallat's algorithm)
is employed. The format of c can be either packed, as returned by the
FWT function or cell-array as returned by WAVPACK2CELL function.
Please see the help on FWT for a detailed description of the parameters.
Examples:
---------
A simple example showing perfect reconstruction:
f = gspi;
J = 8;
c = fwt(f,'db8',J);
fhat = ifwt(c,'db8',J,length(f));
% The following should give (almost) zero
norm(f-fhat)
References:
S. Mallat. A wavelet tour of signal processing. Academic Press, San
Diego, CA, 1998.
Url: http://ltfat.github.io/doc/wavelets/ifwt.html
See also: fwt, wavpack2cell, wavcell2pack.
Package: ltfat