[Insight-users] Problem with Multiplying Two Complex Images, and a big thanks to ITK community for this extensive body of work!

[Dan Mueller]

Hi Saurabh,

Welcome to ITK!

I can't respond regarding your FFT issues/questions, however if your
convolution kernels are small (or computation time is not an issue)
then you may consider computing the convolution directly.

Section 11.4 of the ITK Software Guide describes how to do this using
neighborhood iterators. This part of the software guide is generated
from:
    Examples\Iterators\NeighborhoodIterators4.cxx

HTH

Regards, Dan

2008/11/24 Saurabh Sethi <sethi.saurabh at gmail.com>:
> Hi All,
>
> I recently started using the ITK after a lot of word of mouth publicity from
> peer groups :)
>
> And I must say that im very impressed by it.
>
> Have been going through all of the Software guide and Message Archives since
> some time now.
>
> I have a bit of problem with the FFT / IFFT implementation. There is some
> "Access Violation" that I'm unable to fix since some time.
>
> Maybe I have used the Complex Image in a wrong ( read Silly) way which I'm
> unable to debug now.
>
> It would be great if someone could help ->
>
>
>
> I need to convolve two images (one is the test image, and other is my data
> image)
>
> For this, I had thought of first doing the FFT, then Multiplying both the
> images and taking the IFFT in the end.
>
>
>
> Here is my pseudo code:
>
>
>
> read image 1 (im1)
>
> Padd the image to nearest power of 2.
>
> compute its FFT. (I'm using FFTRealToComplexConjugateImageFilter)
>
>
>
> read image 2. (im2)
>
> Padd the image to the same power of 2.
>
> compute its FFT.
>
>
>
> Multiply both the images
>
> MultiplyImageFilter->SetInput1(fft_input);
>
> MultiplyImageFilter->SetInput2(fft_weight);
>
> MultiplyImageFilter->Update();
>
>
>
> IT is here that this strange error occurs:
>
>
>
> Unhandled exception at 0x0046193a in ItkScatter.exe: 0xC0000005: Access
> violation reading location 0x61371000.
>
>
>
> And the code breaks in at this place  in file
> itkDefaultPixelAccessorFunctor.h:
>
> inline const ExternalPixelType Get( const InternalPixelType & input ) const
>
> {
>
>    return m_PixelAccessor.Get( input );
>
> }
>
>
>
>
>
> Below is the relevant part of the code:
>
>
>
> typedef itk::FFTRealToComplexConjugateImageFilter<pixelTypeC, dim2D>
> FFTFilterType;
>
> typedef itk::FFTComplexConjugateToRealImageFilter<pixelTypeC, dim2D>
> IFFTFilterType;
>
> typedef FFTFilterType::OutputImageType ComplexImageType;
>
> typedef itk::MultiplyImageFilter<ComplexImageType, ComplexImageType,
> ComplexImageType>MultiplyImageFilterType;//>
>
>
>
> constPadImage->SetPadLowerBound(paddin);// specifying padding options
>
> constPadImage->SetPadUpperBound(paddin);
>
> constPadImage->SetInput(inputImage_C); // set padding filter input.
>
> fftFilter->SetInput(constPadImage->GetOutput()); //set the fft.
>
> ComplexImageType::Pointer fft_input = fftFilter->GetOutput(); // fft filter
> done on image.
>
> fftFilter->Update();
>
>
>
> constPadImage2->SetPadUpperBound(paddin_wt_upper);
>
> constPadImage2->SetInput(inputImage2); // set padding filter input.
>
> fft_wtFilter->SetInput(constPadImage2->GetOutput()); //set the fft.
>
> ComplexImageType::Pointer fft_weight= fft_wtFilter->GetOutput();// fft
> filter done on image.
>
> fft_wtFilter->Update();
>
>
>
> MultiplyImageFilter->SetInput1(fft_input);
>
> MultiplyImageFilter->SetInput2(fft_weight);
>
> MultiplyImageFilter->Update() // Error occurs here.
>
> ifftFilter->SetInput(MultiplyImageFilter->GetOutput());
>
> ifftFilter->Update();
>
>
>
> Hi,Many thanks
>
> Saurabh
>
> New ITKer..
>
>
>
>
>
> 2008/11/21 chensiqi <pidanchen at hotmail.com>
>>
>>
>> Hi, ITKers,
>>
>> Does anybody know how to load sequence items using ITK? Such as "ROI
>> Contour Sequence".
>> Or if you know how to do it in GDCM, and integrate into ITK, that will
>> also be very helpful.
>>
>> Thanks
>> Siqi
>>
>>
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>
>
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