sinc.h

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/* Copyright (c) 2008-2022 the MRtrix3 contributors.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Covered Software is provided under this License on an "as is"
 * basis, without warranty of any kind, either expressed, implied, or
 * statutory, including, without limitation, warranties that the
 * Covered Software is free of defects, merchantable, fit for a
 * particular purpose or non-infringing.
 * See the Mozilla Public License v. 2.0 for more details.
 *
 * For more details, see http://www.mrtrix.org/.
 */
 
#ifndef __interp_sinc_h__
#define __interp_sinc_h__
 
#include "types.h"
#include "interp/base.h"
#include "math/sinc.h"
 
 
#define SINC_WINDOW_SIZE 7
 
 
namespace MR
{
  namespace Interp
  {
 
    // @{
 
 
    template <class ImageType> class Sinc : public Base<ImageType>
    { MEMALIGN(Sinc<ImageType>)
      public:
        using typename Base<ImageType>::value_type;
        using Base<ImageType>::out_of_bounds;
        using Base<ImageType>::out_of_bounds_value;
 
        Sinc (const ImageType& parent, value_type value_when_out_of_bounds = Base<ImageType>::default_out_of_bounds_value(), const size_t w = SINC_WINDOW_SIZE) :
            Base<ImageType> (parent, value_when_out_of_bounds),
            window_size (w),
            kernel_width ((window_size-1)/2),
            Sinc_x (w),
            Sinc_y (w),
            Sinc_z (w),
            y_values (w, 0.0),
            z_values (w, 0.0)
        {
          assert (w % 2);
        }
 
 
 
        template <class VectorType>
        bool voxel (const VectorType& pos) {
          if (Base<ImageType>::set_out_of_bounds (pos))
            return false;
          Sinc_x.set (*this, 0, pos[0]);
          Sinc_y.set (*this, 1, pos[1]);
          Sinc_z.set (*this, 2, pos[2]);
          return true;
        }
 
 
        template <class VectorType>
        FORCE_INLINE bool image (const VectorType& pos) {
          return voxel (Transform::voxelsize.inverse() * pos.template cast<default_type>());
        }
 
 
        template <class VectorType>
        FORCE_INLINE bool scanner (const VectorType& pos) {
          return voxel (Transform::scanner2voxel * pos.template cast<default_type>());
        }
 
 
        FORCE_INLINE value_type value () {
          if (out_of_bounds)
            return out_of_bounds_value;
          for (size_t z = 0; z != window_size; ++z) {
            ImageType::index(2) = Sinc_z.index (z);
            for (size_t y = 0; y != window_size; ++y) {
              ImageType::index(1) = Sinc_y.index (y);
              // Cast necessary so that Sinc_x calls the ImageType value() function
              y_values[y] = Sinc_x.value (static_cast<ImageType&>(*this), 0);
            }
            z_values[z] = Sinc_y.value (y_values);
          }
          return Sinc_z.value (z_values);
        }
 
 
        Eigen::Matrix<value_type, Eigen::Dynamic, 1> row (size_t axis) {
          assert (axis > 2);
          assert (axis < ImageType::ndim());
          if (out_of_bounds) {
            Eigen::Matrix<value_type, Eigen::Dynamic, 1> out_of_bounds_row (ImageType::size(axis));
            out_of_bounds_row.setOnes();
            out_of_bounds_row *= out_of_bounds_value;
            return out_of_bounds_row;
          }
 
          Eigen::Matrix<value_type, Eigen::Dynamic, 1> row (ImageType::size(axis));
          // Lazy, non-optimized code, since nothing is actually using this yet
          // Just make use of the kernel setup within voxel()
          for (ssize_t volume = 0; volume != ImageType::size(axis); ++volume) {
            ImageType::index (axis) = volume;
            row (volume,0) = value();
          }
          return row;
        }
 
 
      protected:
        const size_t window_size;
        const int kernel_width;
        Math::Sinc<value_type> Sinc_x, Sinc_y, Sinc_z;
        vector<value_type> y_values, z_values;
 
    };
 
 
 
 
 
  template <class ImageType, typename... Args>
    inline Sinc<ImageType> make_sinc (const ImageType& parent, Args&&... args) {
      return Sinc<ImageType> (parent, std::forward<Args> (args)...);
    }
 
 
 
  }
}
 
#endif