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   -> Volume 6, Issue 7


Question: We are writing a Java-library for wavelet
 
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"Nicolosi Massimo" (nicom@info.isbiel.ch)
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PostPosted: Mon Jul 07, 1997 7:52 am    
Subject: Question: We are writing a Java-library for wavelet
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#22 Question: We are writing a Java-library for wavelet

We are writing a Java-library for wavelet-transformations including the FWT
and IFWT algorithm. There will also be an applet with an easy-to-use
graphical user interface, which will be located on www.isbiel.ch.

We analyzed, how other tools implement the FWT and IFWT-algorithms and
discovered, that different incompatible methods are used. Is there an FWT
algorithm, which is considered the standard FWT?

To explain the different methods we discovered, we attached matrixes
describing the algorithms. As an example we explain two of all discovered
methods.

We would appreciate if you write us your opinion on which you would say is
the standard method (if there is one). Which method would you implement in
our Java library?

Biel School of Engineering
College of the State of Berne (Switzerland)
Computer Science Department
www.isbiel.ch

Urs Kauer (kaueu@info.isbiel.ch)
Massimo Nicolosi (nicom@info.isbiel.ch)

-------------------------------
% Stanford WaveLab MatLab Toolbox ( Stanford University, Palo Alto CA )
% Used Value : Daubechies 4 from Stanford WaveLab MatLab Toolbox
h1 = 0.4830;
h2 = 0.8365;
h3 = 0.2241;
h4 = -0.1294;

%qmf = [h1 h2 h3 h4]
% an = trMh8Std * OrigSIgnal
%low pass h filter from 8 to 4
trMh8Std = [h1 h2 h3 h4 0 0 0 0
0 0 h1 h2 h3 h4 0 0
0 0 0 0 h1 h2 h3 h4
h3 h4 0 0 0 0 h1 h2 ];

%high pass g filter from 8 to 4
trMg8Std = [-h2 h1 0 0 0 0 -h4 h3
-h4 h3 -h2 h1 0 0 0 0
0 0 -h4 h3 -h2 h1 0 0
0 0 0 0 -h4 h3 -h2 h1];

%low pass h filter from 4 to 2
trMh4Std = [h1 h2 h3 h4
h3 h4 h1 h2];

%High pass g filter from 4 to 2
trMg4Std = [-h2 h1 -h4 h3
-h4 h3 -h2 h1];

% IRISA (Institute de recherche en Informatique et Systemes Aleatoires, %
RENNES CEDEX- FRANCE), used Algorithm by published WaveLib (C-library)
% low pass h filter from 8 to 4
trMatrh8 = [h1 0 0 0 0 h4 h3 h2
h3 h2 h1 0 0 0 0 h4
0 h4 h3 h2 h1 0 0 0
0 0 0 h4 h3 h2 h1 0];

% high pass g filter from 8 to 4
trMatrg8 = [0 -h1 h2 -h3 h4 0 0 0
0 0 0 -h1 h2 -h3 h4 0
h4 0 0 0 0 -h1 h2 -h3
h2 -h3 h4 0 0 0 0 -h1];

% low pass h filter from 4 to 2
trMatrh4 = [h1 h4 h3 h2
h3 h2 h1 h4];

% high pass g filter from 4 to 2
trMatrg4 = [h4 -h1 h2 -h3
h2 -h3 h4 -h1];
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