[Insight-users] FFT Confusion

[Cory Quammen]

Gaëtan,

I am currently getting your FFT-based convolution contributions ready
to submit to gerrit, mostly by writing tests for the classes. Once I'm
done with that, I'll do the same for your deconvolution contributions.
Please go ahead and submit the class in question to gerrit if you want
it in today or tomorrow.

Thanks,
Cory

2011/1/25 Gaëtan Lehmann <gaetan.lehmann at jouy.inra.fr>:
>
> I think Cory is working on the integration of this contribution in ITK.
> This class should be part of it.
>
> Cory, if you don't need this class, just let me know and I'll submit it to
> gerrit.
>
> Gaëtan
>
>
> Le 25 janv. 11 à 21:34, Bill Lorensen a écrit :
>
>> Gaëtan ,
>>
>> I suggest submitting this and associated tests to gerrit.
>>
>> Bill
>>
>> 2011/1/25 Gaëtan Lehmann <gaetan.lehmann at jouy.inra.fr>:
>>>
>>> Le 25 janv. 11 à 15:28, David Doria a écrit :
>>>
>>>>> This is the "normal" FFT -- a real image produces a complex image, but
>>>>> there is
>>>>> complex conjugate symmetry of the first half of the transform because
>>>>>
>>>>> sin(-x) = - sin(x) (odd)
>>>>> cos(-x) = cos(x)   (even)
>>>>>
>>>>> exp(ix) = cos(x) + isin(x)
>>>>>
>>>>> This complex conjugate symmetry is sometimes called Hermitian symmetry,
>>>>> but I
>>>>> have been told that is an incorrect term.
>>>>>
>>>>> Regards,
>>>>> Matt
>>>>
>>>> Thanks Matt. Maybe you could explain this in the documentation of the
>>>> class (right now it is basically empty)? (and explain the choice of
>>>> the name of the class too - i.e. why not just VnlFFTImageFilter? ).
>>>>
>>>> Also, should I just use UnaryFunctorImageFilter to compute the complex
>>>> conjugate of the resulting image? I'm surprised not to find a
>>>> ConjugateImageFilter or similar.
>>>
>>> David,
>>>
>>> You will find one at
>>>
>>>
>>>  http://mima2.jouy.inra.fr/darcs/contrib-itk/deconv/itkComplexConjugateImageFilter.h
>>>
>>> Hopefully this class will be in ITK soon.
>>>
>>> Gaëtan
>>>
>>>
>>>> For a normalized correlation of
>>>> images A and B in the frequency domain, I believe you are supposed to
>>>> do
>>>>
>>>> FFT(A) * conj(FFT(B))
>>>>
>>>> Thanks,
>>>>
>>>> David
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>>>
>>> --
>>> Gaëtan Lehmann
>>> Biologie du Développement et de la Reproduction
>>> INRA de Jouy-en-Josas (France)
>>> tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
>>> http://voxel.jouy.inra.fr  http://www.itk.org
>>> http://www.mandriva.org  http://www.bepo.fr
>>>
>>>
>>> _____________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
>>> http://www.kitware.com/opensource/opensource.html
>>>
>>> Kitware offers ITK Training Courses, for more information visit:
>>> http://www.kitware.com/products/protraining.html
>>>
>>> Please keep messages on-topic and check the ITK FAQ at:
>>> http://www.itk.org/Wiki/ITK_FAQ
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.itk.org/mailman/listinfo/insight-users
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>>>
>
> --
> Gaëtan Lehmann
> Biologie du Développement et de la Reproduction
> INRA de Jouy-en-Josas (France)
> tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
> http://voxel.jouy.inra.fr  http://www.itk.org
> http://www.mandriva.org  http://www.bepo.fr
>
>



-- 
Cory Quammen
Computer Integrated Systems for Microscopy and Manipulation (CISMM)
Department of Computer Science
University of North Carolina at Chapel Hill
http://www.cs.unc.edu/~cquammen