[vtkusers] FFT and RFFT problems

[Pascale Beliveau]

Hi,

   I am having problems, applying FFT then RFFT to image. The image is
created using dicom reader and there are no problems with the original data.
But in the result of RFFT I get some intensities as -1.#QNAN00 over the
image. I am trying to find out why that is but cannot find what could be
wrong. Anyone had issues with this already?

Thanks for helping, I've been having this problem for while now and can't
find the problem,
Pascale



Here is the code:

// cast to floating type, vtk fft only works with floats - was unsigned
short before
vtkImageCast * ImCast1 = vtkImageCast::New();
ImCast1->SetInput(VtkImage);
ImCast1->SetOutputScalarTypeToFloat();
ImCast1->Modified();
ImCast1->Update();

// convert using FFT
vtkImageFFT * FFT = vtkImageFFT::New();
FFT->SetDimensionality(3);
FFT->SetInput(ImCast1->GetOutput());
FFT->Modified();
FFT->Update();

// come back to spatial domain
vtkImageRFFT * RFFT = vtkImageRFFT::New();
RFFT->SetDimensionality(3);
RFFT->SetInputConnection(FFT->GetOutputPort());
RFFT->Modified();
RFFT->Update();

vtkImageExtractComponents * RealComponents =
vtkImageExtractComponents::New();
RealComponents->SetInputConnection(RFFT->GetOutputPort());
RealComponents->SetComponents(0); // to fetch the real part of the image,
the imaginary is in component 1
RealComponents->Update();

// Here: RealComponents contain -1.#QNAN00

vtkImageCast * ImCast = vtkImageCast::New();
ImCast->SetInput(RealComponents->GetOutput());
ImCast->SetOutputScalarTypeToUnsignedShort();
ImCast->Modified();
ImCast->Update();

// vtk viewer
vtkImageViewer * viewer = vtkImageViewer::New();
viewer->SetInput(ImCast->GetOutput());
viewer->SetColorWindow(256);
viewer->SetColorLevel(50);
vtkRenderWindowInteractor * viewInt = vtkRenderWindowInteractor::New();
viewer->SetupInteractor(viewInt);
viewer->Render();
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