[vtkusers] need help on vtkImageFFT please

[Cory Quammen]

Stefan,

In any case, the dimensionality *should* be set to 2 regardless of
other settings.

What is the output you get? In MATLAB, I get the following result (all
real values) for your input:

9 0 0
0 0 0
0 0 0

This isn't a surprising result as your test image has a constant value
across all pixels.

Also, make sure you are resetting your variable 'id' to 0 before
entering the loop that prints out the results.

Cory

On Tue, Apr 15, 2008 at 8:13 AM, Stefan  Huber <Huber.Ste at gmx.at> wrote:
> Hi Cory,
>  i also tried it with the dimensionality of 2, but it doesn't work. do you have any other ideas?
>
>  Thanks Stefan
>
>  -------- Original-Nachricht --------
>  > Datum: Tue, 15 Apr 2008 08:07:51 -0400
>  > Von: "Cory Quammen" <cquammen at cs.unc.edu>
>  > An: "Stefan Huber" <Huber.Ste at gmx.at>
>  > CC: vtkusers at vtk.org
>  > Betreff: Re: [vtkusers] need help on vtkImageFFT please
>
>
>
>  > Stefan,
>  >
>  > It looks like  you are setting the wrong dimensionality in the
>  > vtkImageFFT class. You have a 2D image of dimension 3x3, so the
>  > vtkImageFFT class should have dimensionality 2.
>  >
>  > Hope that helps,
>  > Cory
>  >
>  > On Tue, Apr 15, 2008 at 4:39 AM, Stefan  Huber <Huber.Ste at gmx.at> wrote:
>  > > Hi at all,
>  > >
>  > >  Can somebaody help me with vtkImageFFT?
>  > >  I have an ImageDataObject like this:
>  > >    vtkImageData * img = vtkImageData::New()
>  > >    img->SetDimension(3,3,1);
>  > >    img->SetScalarTypeToFloat();
>  > >    img->AllocateScalar();
>  > >
>  > >    float * ptr = (float *) img->GetScalarPointer();
>  > >    for  (int i = 0; i < 3; i++){
>  > >       for (int j = 0; j < 3; j++){
>  > >          *ptr++ = 1;
>  > >       }
>  > >    }
>  > >
>  > >  when i make some Queries on this Dataobject i get the information about
>  > the size and extent.
>  > >    Extent is 0 2 0 2 0 0
>  > >    NumberofComponent = 1
>  > >    Size of Scalar = 9
>  > >
>  > >  Now i want to make a FFT of this image. But the result of the FFT is
>  > very strange and isn't correct. I don't know whats wrong. Please help me.
>  > >  The code for my FFT is this.
>  > >    vtkImageFFT *fft = vtkImageFFT::New();
>  > >    fft->SetDimensionality(1);
>  > >    fft->SetInput(img);
>  > >    fft->Update();
>  > >
>  > >    to print result of FFT:
>  > >    for (i = 0; i < fft->getOutput()->GetNumberofPoints(); i++)
>  > >
>  > im->fft->GetOutput()->GetPointData->GetScalars()->GetComponent(id,1);
>  > >
>  > re->fft->GetOutput()->GetPointData->GetScalars()->GetComponent(id,0);
>  > >      cout << .....
>  > >      id ++;
>  > >   }
>  > >
>  > >  Do you know whats wrong?
>  > >  Thanks Stefan
>  > >
>  > >
>  > >  --
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>  >
>  >
>  > --
>  > Cory Quammen
>  > Department of Computer Science
>  > University of North Carolina at Chapel Hill
>  > http://www.cs.unc.edu/~cquammen
>
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-- 
Cory Quammen
Department of Computer Science
University of North Carolina at Chapel Hill
http://www.cs.unc.edu/~cquammen