Re: Wiki Wavelab

[Stefan van der Walt]

Hi Ken

On Wed, Jul 20, 2005 at 12:41:23PM -0500, Ken Simpson wrote:
>       I = imread('lena256.jpg'); 
>         qmf = MakeONFilter('Symmlet', 8); 
>         [n,J] = dyadlength(I); 
>         wc = FWT2_PO(I, J-1, qmf); 
> 
> This eliminates the error message and generates a image - but the image 
> appears to lack the faint detail expected in "3/4" of the image when 
> viewing the wavelet coefficients matrix with imshow 
> 
>       imshow(wc) 

The wavelet coefficients are much smaller than the scaling
coefficients, which would explain the lack of detail you see.  You
need to normalise the coefficients in order to see them properly (see
the attached functions).

> However, in order to validate the implementation, one needs to at least 
> demostrate perfect reconstruction. 
> 
> When I attempt to reconstruct the image, there are no error messages 
> 
>       I = imread('lena256.jpg');
>         qmf = MakeONFilter('Symmlet', 8); 
>         [n,J] = dyadlength(I); 
>         wc = FWT2_PO(I, J-1, qmf); 
>       iwc = IWT2_PO(wc,J-1,qmf);
> 
> but the inverse transformation behaves as if it were forward 
> transformation.

I am not sure why you have this problem.  On my system, the inverse
transform produces the original image.

Regards
Stéfan

wtplot.m
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wtborders.m
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