text: /*=========================================================================
   *
   *  Copyright Insight Software Consortium
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *         http://www.apache.org/licenses/LICENSE-2.0.txt
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   *=========================================================================*/
  
  //
  // This example was originally contributed by Stephan in the users list
  //
  //     http://public.kitware.com/pipermail/insight-users/2005-June/013482.html
  //
  //
  
  // Software Guide : BeginLatex
  //
  // This example illustrates how to compute the direct Fourier transform
  // followed by the inverse Fourier transform in order to recover the original
  // data.
  //
  // Software Guide : EndLatex
  
  #include "itkImage.h"
  #include "itkImageFileReader.h"
  #include "itkImageFileWriter.h"
  #include "itkResampleImageFilter.h"
  #include "itkVnlForwardFFTImageFilter.h"
  #include "itkVnlInverseFFTImageFilter.h"
  
  int main( int argc, char * argv[] )
  {
    if( argc != 3 )
      {
      std::cerr << "Usage: " << argv[0] << " input output" << std::endl;
      return EXIT_FAILURE;
      }
  
  // Software Guide : BeginLatex
  //
  // First we set up the types of the input and output images.
  //
  // Software Guide : EndLatex
  
  // Software Guide : BeginCodeSnippet
    const   unsigned int      Dimension = 2;
    typedef unsigned short    IOPixelType;
    typedef float             WorkPixelType;
  
    typedef itk::Image< IOPixelType,  Dimension >  IOImageType;
    typedef itk::Image< WorkPixelType, Dimension > WorkImageType;
    // Software Guide : EndCodeSnippet
  
    // File handling
    typedef itk::ImageFileReader< IOImageType > ReaderType;
    typedef itk::ImageFileWriter< IOImageType > WriterType;
  
    ReaderType::Pointer inputreader = ReaderType::New();
    WriterType::Pointer writer = WriterType::New();
  
    inputreader->SetFileName( argv[1] );
    writer->SetFileName( argv[2] );
  
    // Handle padding of the image with resampling
    typedef itk::ResampleImageFilter<
                                IOImageType,
                                WorkImageType >  ResamplerType;
  
    ResamplerType::Pointer inputresampler = ResamplerType::New();
    inputresampler->SetDefaultPixelValue(0);
  
    // Read the image and get its size
    inputreader->Update();
  
    IOImageType::SizeType     inputsize;
    IOImageType::SizeType     worksize;
  
    inputsize = inputreader->GetOutput()->GetLargestPossibleRegion().GetSize();
  
    // worksize is the nearest multiple of 2 larger than the input
    for( unsigned int i=0; i < 2; i++ )
      {
      unsigned int n=0;
      worksize[i] = inputsize[i];
      while( worksize[i] >>= 1 )
        {
        n++;
        }
      worksize[i] = static_cast<IOImageType::SizeValueType> ( 1 )
        << static_cast<IOImageType::SizeValueType>( n + 1 );
  
      std::cout << "inputsize[" << i << "]=" << inputsize[i] << std::endl;
      std::cout << "worksize[" << i << "]=" << worksize[i] << std::endl;
      }
  
    inputresampler->SetSize( worksize );
    inputresampler->SetInput( inputreader->GetOutput() );
  
    // Forward FFT filter
    typedef itk::VnlForwardFFTImageFilter < WorkImageType > FFTFilterType;
    FFTFilterType::Pointer fftinput = FFTFilterType::New();
    fftinput->SetInput( inputresampler->GetOutput() );
  
    // This is the output type from the FFT filters
    typedef FFTFilterType::OutputImageType ComplexImageType;
  
    // Do the inverse transform = forward transform / num voxels
    typedef itk::VnlInverseFFTImageFilter < ComplexImageType > invFFTFilterType;
    invFFTFilterType::Pointer fftoutput = invFFTFilterType::New();
    fftoutput->SetInput(fftinput->GetOutput()); // try to recover the input image
  
    // undo the padding
    typedef itk::ResampleImageFilter<WorkImageType, IOImageType> ResampleOutType;
    ResampleOutType::Pointer outputResampler = ResampleOutType::New();
    outputResampler->SetDefaultPixelValue( 0 );
    outputResampler->SetSize( inputsize );
    outputResampler->SetInput( fftoutput->GetOutput() );
  
    // Write the output
    writer->SetInput(outputResampler->GetOutput());
    writer->Update();
  
    return EXIT_SUCCESS;
  }
  