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> Volume 7, Issue 6
Question: Wavelet coefficients in terms of shift and scale

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Madhavi Kadiyala (mkadiyal@lincoln.ecn.ou.edu) Guest

Posted: Thu Jun 11, 1998 10:25 pm Subject: Question: Wavelet coefficients in terms of shift and scale




#27 Question: Wavelet coefficients in terms of shift and scale
Hi!,
I was trying to caculate discrete wavelet transform
coefficients (dwt) as a function of shift (n) and scale (m). So, I was
using the basic double integral equation as function of m and n to
calculate the dwt coefficients for 1D data. But, they have to be same
as the dwt coefficients calculated using filter banks, except that
they are arranged in a different format. So, I used the matlab wavelet
toolbox to calculate the dwt coefficients and I wrote a function to
calculate the same using the double integral. I am getting the same
values for haar but not for Daubechies. I don't know why. It looks
like a simple integration (sum). Could you please help me with this?
I want to do the same for 2D (image) data. Then the coefficients
are 4D if they are to be expressed in terms of m and n, i.e. mx, nx, my
and ny. I want to use separable wavelet, because it is simple. If I apply
1D wavelet on each row of NxN image, the coefficients are N * mx * nx.
Now, if I do the same, i.e. apply 1D wavelet on each column of the
N * mx * nx matrix, N * nx * my * ny not mx * my * nx * ny. How I can I
get that? What is the mistake I am doing? Could you please clarify my
doubts?
Thanks,
Madhavi. 





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