itkRectangularImageNeighborhoodShape.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 itkRectangularImageNeighborhoodShape_h
#define itkRectangularImageNeighborhoodShape_h
 
#include <algorithm> // For transform.
#include <cassert>
 
#include "itkOffset.h"
#include "itkSize.h"
 
namespace itk
{
 
template <unsigned int VImageDimension>
class RectangularImageNeighborhoodShape
{
public:
  static constexpr unsigned int ImageDimension = VImageDimension;
  constexpr explicit RectangularImageNeighborhoodShape(const Size<ImageDimension> & radius) noexcept
    : m_Radius(radius)
    , m_NumberOfOffsets(CalculateNumberOfOffsets(ImageDimension))
  {}
 
 
  constexpr size_t
  GetNumberOfOffsets() const noexcept
  {
    return m_NumberOfOffsets;
  }
 
 
  void
  FillOffsets(Offset<ImageDimension> * const offsets) const noexcept
  {
    if (m_NumberOfOffsets > 0)
    {
      assert(offsets != nullptr);
      Offset<ImageDimension> offset;
      std::transform(m_Radius.begin(), m_Radius.end(), offset.begin(), [](const SizeValueType radiusValue) {
        return -static_cast<OffsetValueType>(radiusValue);
      });
 
      for (size_t i = 0; i < m_NumberOfOffsets; ++i)
      {
        offsets[i] = offset;
 
        for (unsigned int dimensionIndex = 0; dimensionIndex < ImageDimension; ++dimensionIndex)
        {
          OffsetValueType & offsetValue = offset[dimensionIndex];
 
          ++offsetValue;
 
          if (offsetValue <= static_cast<OffsetValueType>(m_Radius[dimensionIndex]))
          {
            break;
          }
          offsetValue = -static_cast<OffsetValueType>(m_Radius[dimensionIndex]);
        }
      }
    }
  }
 
private:
  // The radius of the neighborhood along each direction.
  Size<ImageDimension> m_Radius;
 
  // The number of offsets needed to represent this shape.
  size_t m_NumberOfOffsets;
 
 
  // Private helper function to calculate the number of Offsets by a recursive
  // function call. Recursion is necessary for C++11 constexpr.
  constexpr size_t
  CalculateNumberOfOffsets(const unsigned int dimension) const noexcept
  {
    return (dimension == 0)
             ? 1
             : (2 * m_Radius.m_InternalArray[dimension - 1] + 1) * CalculateNumberOfOffsets(dimension - 1);
  }
};
 
} // namespace itk
 
#endif