[Insight-users] FFT Confusion

[Gaëtan Lehmann]

Le 25 janv. 11 à 22:29, Cory Quammen a écrit :

> 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.


If I get a chance, I'll try to do it in the next days, but I don't  
think we are in a hurry.

Gaëtan

>
> 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
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>>>>
>>>> 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:
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>>>>
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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

-- 
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

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