itkPocketFFTCommon.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://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.
 *
 *=========================================================================*/
#ifndef itkPocketFFTCommon_h
#define itkPocketFFTCommon_h
 
#include "pocketfft_hdronly.h"
 
namespace itk
{
namespace PocketFFTCommon
{

template <typename TSize>
inline pocketfft::shape_t
MakeShape(const TSize & itkSize, const unsigned int dimension)
{
  pocketfft::shape_t shape(dimension);
  for (unsigned int i = 0; i < dimension; ++i)
  {
    shape[dimension - 1 - i] = itkSize[i];
  }
  return shape;
}

template <typename TSize>
inline pocketfft::stride_t
MakeStride(const TSize & itkSize, const unsigned int dimension, const size_t pixelBytes)
{
  pocketfft::stride_t stride(dimension);
  ptrdiff_t           byteStride = static_cast<ptrdiff_t>(pixelBytes);
  for (unsigned int i = 0; i < dimension; ++i)
  {
    stride[dimension - 1 - i] = byteStride;
    byteStride *= static_cast<ptrdiff_t>(itkSize[i]);
  }
  return stride;
}

inline pocketfft::shape_t
MakeAxes(const unsigned int dimension)
{
  pocketfft::shape_t axes(dimension);
  for (unsigned int i = 0; i < dimension; ++i)
  {
    axes[i] = i;
  }
  return axes;
}

template <typename TValue>
inline void
Transform1D(std::complex<TValue> * data, const size_t lineLength, const bool forward, const TValue scale)
{
  const pocketfft::shape_t  shape{ lineLength };
  const pocketfft::stride_t stride{ static_cast<ptrdiff_t>(sizeof(std::complex<TValue>)) };
  pocketfft::c2c(shape, stride, stride, { 0 }, forward, data, data, scale);
}
 
} // namespace PocketFFTCommon
} // namespace itk
 
#endif