[Insight-users] Forward + Inverse FFT != Identity transform

[Jakub Bican]

Hi,

i had a problem with linking FFTW too (on MSVC 7 platform), and my 
solution is to replace

       LINK_DIRECTORIES( ${FFTW_LIB} )

line #35 with

       LINK_LIBRARIES( ${FFTW_LIB} )

in

       Insight/CMake/FindFFTW.cmake

file, as i posted several weeks ago. May be, it will help you too. Are 
there any opinions to this by ITK team?


Cheers,

             Jakub



Julien Jomier napsal(a):

> Hi Jordi,
>
> Actually the fix for gcc 3.4 was submitted after the 2.0.1 release. 
> You can use the cvs version of ITK if you want.
>
> Did you enable USE_FFTW when running CMake on Insight?
> Can you post the linker errors you are getting?
>
> thanks,
>
> Julien
>
> Jordi Inglada wrote:
>
>>
>> Julien,
>>
>> Thanks for your answer.
>>
>> Julien Jomier wrote:
>>
>>> Jordi, Stefan,
>>>
>>> We had the same issue here. One solution was to use FFTW and the
>>> corresponding FFTW classes in ITK.
>>>
>>
>> I have just tried, but now is FFTW (version 3) which causes trouble. 
>> First of all I had to add the following lines to 
>> itkFFTWRealToComplexConjugateImageFilter.h in order to compile with 
>> gcc 3.4 :
>>
>> typedef typename Superclass::TInputImageType TInputImageType;
>>  typedef typename Superclass::TOutputImageType TOutputImageType;
>>
>> And now, the the fftwf_* functions seem not to be present into the 
>> libfftw3.a file (at least, ld is no able to find them and 'nm 
>> libfftw3.a |grep fftwf' says nothing).
>>
>>> We didn't have time to dig into the possible bug using the VNL classes.
>>> Did you submit a bug report on the bug tracker (www.itk.org/bug) yet?
>>>
>>
>> Not yet.
>>
>> Jordi
>>
>>> Julien
>>>
>>> Jordi Inglada wrote:
>>> > Dear Stefan, all,
>>> >
>>> > Has there been a proposed solution to this problem? We are having
>>> > similar problems : the FFT of a sinusoidal surface has not the 
>>> expected
>>> > shape (see the real, imaginary, and module parts of the FFT). We have
>>> > used the FFTImageFilter.cxx example.
>>> >
>>> > Thanks for any advice.
>>> >
>>> > J. Inglada
>>> >
>>> > group at spellgen.com wrote:
>>> >
>>> >> Trying to debug a convolution routine for two images based on 
>>> Fourier
>>> >> transforms, I find that a forward FFT immediately followed by its
>>> >> inverse does
>>> >> not produce the image I started with. The code looks straightforward
>>> >> enough -
>>> >> it does the following:
>>> >> 1. Read the image from a grayscale char-type file
>>> >> 2. Resample to width and height both being powers of two.
>>> >> 3. Forward transform (float)
>>> >> 4. Another forward transform.
>>> >> 5. Flip data in both dimensions
>>> >> 6. Rescale to bring it into char range again
>>> >> 7 Write the image.
>>> >>
>>> >> urls for the input (black with a white dot at the origin) and the 
>>> output
>>> >> images:
>>> >> http://neuromagnetics.mc.vanderbilt.edu/out/itk/point.png
>>> >> http://neuromagnetics.mc.vanderbilt.edu/out/itk/out.png
>>> >>
>>> >> The source code is there as well:
>>> >> http://neuromagnetics.mc.vanderbilt.edu/out/itk/four2-example.cxx
>>> >>
>>> >> Any suggestions as to what is going on would be appreciated...
>>> >>
>>> >> Cheers,
>>> >>
>>> >> Stefan
>>> >>
>>> >>
>>> >>
>>> >> _______________________________________________
>>> >> Insight-users mailing list
>>> >> Insight-users at itk.org
>>> >> http://www.itk.org/mailman/listinfo/insight-users
>>> >>
>>> >
>>> >
>>> >
>>> > 
>>> ------------------------------------------------------------------------ 
>>>
>>> >
>>> >
>>> > 
>>> ------------------------------------------------------------------------ 
>>>
>>> >
>>> >
>>> > 
>>> ------------------------------------------------------------------------ 
>>>
>>> >
>>> >
>>> > 
>>> ------------------------------------------------------------------------ 
>>>
>>> >
>>> >
>>> > 
>>> ------------------------------------------------------------------------ 
>>>
>>> >
>>> > _______________________________________________
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>>> > Insight-users at itk.org
>>> > http://www.itk.org/mailman/listinfo/insight-users
>>>
>>
>>
>
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