Filter.h

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//
//

/*
    Copyright (C) 2000 PARAPET partners
    SPDX-License-Identifier: Apache-2.0
    Copyright (C) 2000- 2002, IRSL
    See STIR/LICENSE.txt for details
*/

#ifndef __FILTER_H__
#define __FILTER_H__

#include "stir/TimedObject.h"
#include "stir/Array.h"
#include "stir_experimental/fft.h"
#include <string>

START_NAMESPACE_STIR

template <int num_dimensions, typename elemT>
class Array;

template <class T>
class Filter1D : public TimedObject
{
  // AZ public, as need to access length for parallel FBP3DRP code  (TODO)
  // protected:
public:
  Array<1, float> filter;

public:
  Filter1D(const int length_v)
      : filter(1, length_v)
  {}
  Filter1D(const Array<1, T>& filter)
      : filter(filter)
  {}
  virtual ~Filter1D() {}


  inline void apply(Array<1, T>& data);
  inline void apply(Array<2, T>& data);
  inline void apply(Array<3, T>& data);

  virtual std::string parameter_info() const = 0;
};

// TODO can't be const due to start_timers()
template <class T>
void
Filter1D<T>::apply(Array<1, T>& data) // const
{
  start_timers();
  const int length = filter.get_length();
  if (length == 0)
    return;
  assert(length > 0);

  Array<1, T> Padded = data;
  Padded.set_offset(1);
  Padded.grow(1, length);
  convlvC(Padded, filter, length);

  Padded.set_offset(data.get_min_index());

  for (int j = data.get_min_index(); j <= data.get_max_index(); j++)
    data[j] = Padded[j];

  stop_timers();
}

template <class T>
void
Filter1D<T>::apply(Array<2, T>& data) // const
{
  for (int i = data.get_min_index(); i <= data.get_max_index(); i++)
    apply(data[i]);
}

template <class T>
void
Filter1D<T>::apply(Array<3, T>& data) // const
{
  for (int i = data.get_min_index(); i <= data.get_max_index(); i++)
    apply(data[i]);
}

template <class T>
class Filter2D : public TimedObject
{
public:
  Filter2D(int height_v, int width_v)
      : height(height_v),
        width(width_v),
        filter(1, width_v * height_v)
  {}

  virtual ~Filter2D() {}
  inline void apply(Array<1, T>& data) const;

  // TODO ???
  void padd_scale_filter(int height_proj, int width_proj);

  virtual std::string parameter_info() const = 0;

protected:
  int height;
  int width;

  Array<1, T> filter;
};

template <class T>
void
Filter2D<T>::apply(Array<1, T>& data) const
{

  assert(data.get_length() == 2 * height * width);

  assert(data.get_min_index() == 1);

  int j, k;
  /*TODO copy lines from Filter_proj_Colsher for this convertion, and call apply with a Array<2,T>
  Array<1,T> data(1, 2*height*width);

  for (int h = 1, j=1; h <= data2d.height(); h++)
    for (int w=1; w <= data2d.get_width(); w++) {
      data[j++] = data2d[h][w];
    }
    */

  Array<1, int> nn(1, 2);
  nn[1] = height;
  nn[2] = width;
  fourn(data, nn, 2, 1);
  for (j = 1, k = 1; j < width * height + 1; j++)
    {
      // KT 11/04/2000 normalise with total length
      // divide by width*height to take Num Recipes convention into account that the
      // 'inverse' Fourier transform needs scaling by the total number of data points.
      data[k++] *= filter[j] / (width * height);
      data[k++] *= filter[j] / (width * height);
    }
  fourn(data, nn, 2, -1);
};

END_NAMESPACE_STIR

#endif