[Insight-users] FFTWComplexConjugateToRealImageFilter gives output 2 times the size of input

[Amit Mukherjee]

Hi all,

I was doing FFTW in ITK and I was using the following code for an input 
size [200, 200, 100] ..


typedef float PixelType;
typedef itk::Image< PixelType, 3 >	ImageType3D;
typedef itk::FFTWComplexConjugateToRealImageFilter <PixelType, 3 > 
invFFTFilterType;

invFFTFilterType::Pointer ifft = invFFTFilterType::New();
ifft->SetInput(complexInput);
ImageType3D::Pointer vols = ifft->GetOutput();
vols->Update();

In the above code "complexInput" is a [200, 200, 100] 
itk::Image<std::complex<float>,3> data obtained due to some operation. I 
just need the real part of the IFFT as output. But I observe that "vols" 
in the above code is of size [398, 200, 100] ...

Any idea why the size is increasing and how the data (real and complex) 
is arranged within..

Amit