MaxentTransformFourier.cpp

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#include "MantidAlgorithms/MaxEnt/MaxentTransformFourier.h"
#include <utility>
 
#include <gsl/gsl_fft_complex.h>
#include <memory>
#include <stdexcept>
 
#include <stdexcept>
 
namespace Mantid::Algorithms {
 
MaxentTransformFourier::MaxentTransformFourier(MaxentSpace_sptr dataSpace, MaxentSpace_sptr imageSpace)
    : m_dataSpace(std::move(dataSpace)), m_imageSpace(std::move(imageSpace)) {}
 
std::vector<double> MaxentTransformFourier::imageToData(const std::vector<double> &image) {
 
  std::vector<double> complexImage = m_imageSpace->toComplex(image);
 
  /* Performs backward Fourier transform */
 
  size_t n = complexImage.size();
 
  if (n % 2) {
    throw std::invalid_argument("Cannot transform to data space");
  }
 
  /* Backward FT */
  gsl_fft_complex_wavetable *wavetable = gsl_fft_complex_wavetable_alloc(n / 2);
  gsl_fft_complex_workspace *workspace = gsl_fft_complex_workspace_alloc(n / 2);
  gsl_fft_complex_inverse(complexImage.data(), 1, n / 2, wavetable, workspace);
  gsl_fft_complex_wavetable_free(wavetable);
  gsl_fft_complex_workspace_free(workspace);
 
  return m_dataSpace->fromComplex(complexImage);
}
 
std::vector<double> MaxentTransformFourier::dataToImage(const std::vector<double> &data) {
 
  std::vector<double> complexData = m_dataSpace->toComplex(data);
 
  /* Performs forward Fourier transform */
 
  size_t n = complexData.size();
 
  if (n % 2) {
    throw std::invalid_argument("Cannot transform to image space");
  }
 
  /*  Fourier transofrm */
  gsl_fft_complex_wavetable *wavetable = gsl_fft_complex_wavetable_alloc(n / 2);
  gsl_fft_complex_workspace *workspace = gsl_fft_complex_workspace_alloc(n / 2);
  gsl_fft_complex_forward(complexData.data(), 1, n / 2, wavetable, workspace);
  gsl_fft_complex_wavetable_free(wavetable);
  gsl_fft_complex_workspace_free(workspace);
 
  return m_imageSpace->fromComplex(complexData);
}
 
} // namespace Mantid::Algorithms