[Insight-users] ifft

[Jesse C Cronce]

I think that the problem that I was seeing is that the results that are
returned are no longer complex numbers, but the phase is still infused
in the array. After going through the fftw website, I saw what I think
it was that the filter was returning. For what I'm doing, though, I did
the ifft "by hand" and then used the ImportImageFilter to get images.

Thanks!
JCC

On Tue, 2005-10-25 at 02:09 -0400, Luis Ibanez wrote:
> Hi Jesse,
> 
> By "normalization" do you mean Intensity Normalization ?
> 
> If so, yes, ITK provides multiple filters for preforming
> linear operations on the intensities of the image.
> 
> You may want to look at the ITK Software Guide
> 
>      http://www.itk.org/ItkSoftwareGuide.pdf
> 
> and search for the filters:
> 
>      IntensityWindowingImageFilter
>      ShiftScaleImageFilter
>      NormalizeImageFilter
> 
> 
> However, I don't quite see how this normalization will
> help with the problem of image dimensions that you
> describe....
> 
> 
> 
> Regards,
> 
> 
> 
>     Luis
> 
> 
> 
> ---------------------
> Jesse C Cronce wrote:
> > Thanks Carlos, that helped a lot.
> > 
> > I did that, and what the FFTW outputs is a lot closer to what I really
> > want than the VnlFFT was outputting. However, the FFTW inverse fourier
> > transform returns an image that is scaled - if I pass in an image that
> > is 128 x 512 (complex floats), the output image is 128 x 1022. 
> > 
> > According to the documentation on the FFTW website, what I want is an
> > image that has been normalized (which is apparently what matlab does).
> > Does ITK provide an easy way to do this ? Or is it a simple matter of
> > moving the pixels around to get the correct image ? Any suggestions
> > would be greatly appreciated.
> > 
> > Thanks,
> > JCC
> > 
> > On Wed, 2005-10-12 at 08:52 -0300, Carlos Santos wrote:
> > 
> >>Hi,
> >>
> >>There are some reports of problems with the VnlFFT classes, the
> >>suggested solution is using FFTW (http://fftw.org/) instead.
> >>See:
> >>http://www.itk.org/pipermail/insight-users/2005-July/013900.html
> >>for a more thorough discussion.
> >>
> >>Hope this helps,
> >>Carlos
> >>
> >>On 10/11/05, Jesse C Cronce <croncejc at mrctr.upmc.edu> wrote:
> >>
> >>>All,
> >>>
> >>>    Does anyone know if there is an equivalent call to the Matlab call
> >>>ifft2 in ITK ?
> >>>
> >>>When I compare values computed by ifft2 in matlab on an identical matrix
> >>>that I put through the itkVnlFFTComplexConjugateToRealImageFilter the
> >>>pixel values are extremely different.
> >>>
> >>>Thanks,
> >>>JCC
> >>>
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> >>>
> > 
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