ArrayFilterUsingRealDFTWithPadding.h

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/*
    Copyright (C) 2004-2009, Hammersmith Imanet Ltd
    This file is part of STIR.

    SPDX-License-Identifier: Apache-2.0

    See STIR/LICENSE.txt for details
*/

#ifndef __stir_ArrayFilterUsingRealDFTWithPadding_H__
#define __stir_ArrayFilterUsingRealDFTWithPadding_H__

#include "stir/Array.h"
#include "stir/ArrayFunctionObject_2ArgumentImplementation.h"
#include "stir/Array_complex_numbers.h"
#include "stir/IndexRange.h"
#include <complex>

START_NAMESPACE_STIR
class Succeeded;

template <int num_dimensions, typename elemT>
class ArrayFilterUsingRealDFTWithPadding : public ArrayFunctionObject_2ArgumentImplementation<num_dimensions, elemT>
{
public:
  ArrayFilterUsingRealDFTWithPadding();

  ArrayFilterUsingRealDFTWithPadding(const Array<num_dimensions, elemT>& real_filter_kernel);


  ArrayFilterUsingRealDFTWithPadding(const Array<num_dimensions, std::complex<elemT>>& kernel_in_frequency_space);

  /*
    The kernel can be given with arbitrary (but regular) index range,
    but will be wrapped-around,
      assuming that it is periodic outside the indexrange of the kernel. So,
      normally, the 0- index corresponds to the middle of the PSF.

      Input data will be zero-padded to the same range as this kernel before
      DFT. If you want to avoid aliasing, make sure that the kernel is at least
      twice as long as the input and output arrays.

      As this function uses fourier_for_real_data(), see there for restrictions
      on the possible kernel length, but at time of writing, it has to be a power of 2.
  */
  Succeeded set_kernel(const Array<num_dimensions, elemT>& real_filter_kernel);

  /*  The kernel has to be given with index ranges starting from 0.
      So, the 0- index corresponds to the DC component of the filter.

      \see fourier_for_real_data() for more info on the range of frequencies
      Input data will be zero-padded to the index range as the corresponding
      'real' kernel before DFT. If you want to avoid aliasing, make sure that the kernel is at least
      twice as long as the input and output arrays.

      See fourier() for restrictions on the possible
      kernel length, but at time of writing, it has to be a power of 2.
  */
  Succeeded set_kernel_in_frequency_space(const Array<num_dimensions, std::complex<elemT>>& kernel_in_frequency_space);


  bool is_trivial() const override;

protected:
  Array<num_dimensions, std::complex<elemT>> kernel_in_frequency_space;


  void do_it(Array<num_dimensions, elemT>& out_array, const Array<num_dimensions, elemT>& in_array) const override;

private:
  IndexRange<num_dimensions> padding_range;
  BasicCoordinate<num_dimensions, int> padded_sizes;
  Succeeded set_padding_range();
};

END_NAMESPACE_STIR

#endif // ArrayFilterUsingRealDFTWithPadding