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

[Kevin H. Hobbs]

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 think most of what I'm worried about only comes into play when
I have to write out the magnitude image, convert it to a
meta-data destroying format, print it show it to my boss, create
a mask in the gimp...

I put all of the meta-data back into the mask except I can't
change its size so the Largest possible regions don't line up
unless I write out the full image with
UpdateLargestPossibleRegion on the writer.

I just want to make sure there's a documented way for the user to
avoid potential headaches.


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