[Insight-developers] Consistency in the output of forward/inverse FFT image filters

[Gaëtan Lehmann]

Le 19 août 11 à 12:05, Kevin H. Hobbs a écrit :

> On 08/18/2011 08:38 PM, Cory Quammen wrote:
>> [snip]
>>
>>> 3.   to do anything useful with the frequency domain image I need
>>> to apply an asymmetrical mask.
>> I take this to mean that you need the full frequency domain image,  
>> then?
>
> Err.. I may have used "asymmetrical" stupidly.
>
> I, at least, only got good results when I masked a weird looking
> blob.
>
> That blob was symmetrical across the center of the image.
>
> It just wasn't a pretty little Gaussian .
>
> The mask filter complained when I had a half image mask for the
> half frequency domain image.
>
> The mask filter has no way of knowing that the rest of the
> LargestPossibleRegion won't be used.
>
>
>>
>>> So if there is going to be work done on the FFT filters I would
>>> like to make sure that shifting, and masking work. I'd be willing
>>> to work on the test or at least example code.
>> Does FFTShiftImageFilter not work? It appeared to work fine for the
>> code sample you provided when VNL was used for the FFT.
>>
>
>
> Would it work for only half of the image, or would it put the
> corners of the half image in the middle of the half image?


I'm quite sure it won't do what you expect: the half dimension will be  
shifted as well.

But does it make sense to run it on a half image?
If yes then I guess an option should be added to the fft shift filter  
to make it work as expected.

Regards,

Gaëtan


-- 
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://mima2.jouy.inra.fr  http://www.itk.org
http://www.bepo.fr

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