ITK/Examples/SpectralAnalysis/VnlFFTRealToComplexConjugateImageFilter

VnlFFTRealToComplexConjugateImageFilter.cxx

<source lang="cpp">

1. include "itkImage.h"
2. if ITK_VERSION_MAJOR < 4
3. include "itkVnlFFTRealToComplexConjugateImageFilter.h"
4. else
5. include "itkVnlForwardFFTImageFilter.h"
6. endif
7. include "itkComplexToRealImageFilter.h"
8. include "itkComplexToImaginaryImageFilter.h"
9. include "itkComplexToModulusImageFilter.h"
10. include "itkImageFileReader.h"
11. include "itkPasteImageFilter.h"

1. include <itksys/SystemTools.hxx>
2. include "vnl/vnl_sample.h"
3. include <math.h>

1. include <itkImageToVTKImageFilter.h>

1. include "QuickView.h"

int main(int argc, char*argv[]) {

 // Verify input
 if(argc < 2)
   {
   std::cerr << "Required: filename" << std::endl;
   return EXIT_FAILURE;
   }

 // Define some types
 typedef itk::Image<float, 2> FloatImageType;

 // Read the image
 typedef itk::ImageFileReader<FloatImageType> ReaderType;
 ReaderType::Pointer reader = ReaderType::New();
 reader->SetFileName(argv[1]);
 reader->Update();

 // Compute the smallest power of two that is bigger than the image
 unsigned int powerOfTwo = 0;
 for(unsigned int i = 0; i < 20; i++)
   {
   if(pow(2.0, static_cast<double>(i)) >= reader->GetOutput()->GetLargestPossibleRegion().GetSize()[0] &&
      pow(2.0, static_cast<double>(i)) >= reader->GetOutput()->GetLargestPossibleRegion().GetSize()[1])
     {
     powerOfTwo = i;
     break;
     }
   }

 // Create an image bigger than the input image and that has
 // dimensions which are powers of two
 itk::Index<2> start;
 start.Fill(0);

 itk::Size<2> size;
 size.Fill(pow(2.0,static_cast<double>(powerOfTwo)));

 itk::ImageRegion<2> region(start, size);

 FloatImageType::Pointer image = FloatImageType::New();
 image->SetRegions(region);
 image->Allocate();
 image->FillBuffer(0);

 // The image dimensions must be powers of two
 typedef itk::PasteImageFilter <FloatImageType, FloatImageType >
   PasteImageFilterType;
 itk::Index<2> destinationIndex;
 destinationIndex.Fill(0);
 
 PasteImageFilterType::Pointer pasteFilter
   = PasteImageFilterType::New ();
 pasteFilter->SetSourceImage(reader->GetOutput());
 pasteFilter->SetDestinationImage(image);
 pasteFilter->SetSourceRegion(reader->GetOutput()->GetLargestPossibleRegion());
 pasteFilter->SetDestinationIndex(destinationIndex);
 pasteFilter->Update();
 
 image->Graft(pasteFilter->GetOutput());
 
 // Compute the FFT

1. if ITK_VERSION_MAJOR < 4

 typedef itk::VnlFFTRealToComplexConjugateImageFilter<FloatImageType> FFTType;

1. else

 typedef itk::VnlForwardFFTImageFilter<FloatImageType> FFTType;

1. endif

 FFTType::Pointer fftFilter = FFTType::New();
 fftFilter->SetInput(image);
 
 // Extract the real part
 typedef itk::ComplexToRealImageFilter<FFTType::OutputImageType, FloatImageType> RealFilterType;
 RealFilterType::Pointer realFilter = RealFilterType::New();
 realFilter->SetInput(fftFilter->GetOutput());

 // Extract the complex part
 typedef itk::ComplexToImaginaryImageFilter<FFTType::OutputImageType, FloatImageType> ImaginaryFilterType;
 ImaginaryFilterType::Pointer imaginaryFilter = ImaginaryFilterType::New();
 imaginaryFilter->SetInput(fftFilter->GetOutput());

 // Compute the magnitude
 typedef itk::ComplexToModulusImageFilter<FFTType::OutputImageType, FloatImageType> ModulusFilterType;
 ModulusFilterType::Pointer modulusFilter = ModulusFilterType::New();
 modulusFilter->SetInput(fftFilter->GetOutput());

 QuickView viewer;
 viewer.AddImage(image.GetPointer(), true,
   itksys::SystemTools::GetFilenameName(argv[1]));
 viewer.AddImage(realFilter->GetOutput(), true,
   "Real");
 viewer.AddImage(imaginaryFilter->GetOutput(), true,
   "Imaginary");
 viewer.AddImage(modulusFilter->GetOutput(), true,
   "Magnitude");
 viewer.Visualize();

 return EXIT_SUCCESS;

} </source>

CMakeLists.txt

<syntaxhighlight lang="cmake"> cmake_minimum_required(VERSION 3.9.5)

project(VnlFFTRealToComplexConjugateImageFilter)

find_package(ITK REQUIRED) include(${ITK_USE_FILE}) if (ITKVtkGlue_LOADED)

 find_package(VTK REQUIRED)
 include(${VTK_USE_FILE})

else()

 find_package(ItkVtkGlue REQUIRED)
 include(${ItkVtkGlue_USE_FILE})
 set(Glue ItkVtkGlue)

endif()

add_executable(VnlFFTRealToComplexConjugateImageFilter MACOSX_BUNDLE VnlFFTRealToComplexConjugateImageFilter.cxx) target_link_libraries(VnlFFTRealToComplexConjugateImageFilter

 ${Glue}  ${VTK_LIBRARIES} ${ITK_LIBRARIES})

</syntaxhighlight>

Download and Build VnlFFTRealToComplexConjugateImageFilter

Click here to download VnlFFTRealToComplexConjugateImageFilter. and its CMakeLists.txt file. Once the tarball VnlFFTRealToComplexConjugateImageFilter.tar has been downloaded and extracted,

cd VnlFFTRealToComplexConjugateImageFilter/build 

• If ITK is installed:

cmake ..

• If ITK is not installed but compiled on your system, you will need to specify the path to your ITK build:

cmake -DITK_DIR:PATH=/home/me/itk_build ..

Build the project,

make

and run it:

./VnlFFTRealToComplexConjugateImageFilter

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK and ITK bin directories to your path. This will resolve the VTK and ITK dll's at run time.

Building All of the Examples

Many of the examples in the ITK Wiki Examples Collection require VTK. You can build all of the the examples by following these instructions. If you are a new VTK user, you may want to try the Superbuild which will build a proper ITK and VTK.

ItkVtkGlue

ITK >= 4

For examples that use QuickView (which depends on VTK), you must have built ITK with Module_ITKVtkGlue=ON.

ITK < 4

Some of the ITK Examples require VTK to display the images. If you download the entire ITK Wiki Examples Collection, the ItkVtkGlue directory will be included and configured. If you wish to just build a few examples, then you will need to download ItkVtkGlue and build it. When you run cmake it will ask you to specify the location of the ItkVtkGlue binary directory.