itkConstantBoundaryImageNeighborhoodPixelAccessPolicy.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.
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#ifndef itkConstantBoundaryImageNeighborhoodPixelAccessPolicy_h
#define itkConstantBoundaryImageNeighborhoodPixelAccessPolicy_h
 
#include "itkIndex.h"
#include "itkOffset.h"
#include "itkSize.h"
 
namespace itk
{
 
template <typename TImage>
class ConstantBoundaryImageNeighborhoodPixelAccessPolicy final
{
private:
  using NeighborhoodAccessorFunctorType = typename TImage::NeighborhoodAccessorFunctorType;
  using PixelType = typename TImage::PixelType;
  using InternalPixelType = typename TImage::InternalPixelType;
 
  using ImageDimensionType = typename TImage::ImageDimensionType;
  static constexpr ImageDimensionType ImageDimension = TImage::ImageDimension;
 
  using IndexType = Index<ImageDimension>;
  using OffsetType = Offset<ImageDimension>;
  using ImageSizeType = Size<ImageDimension>;
  using ImageSizeValueType = SizeValueType;
 
  // Index value to the image buffer, indexing the current pixel. -1 is used to indicate out-of-bounds.
  const IndexValueType m_PixelIndexValue;
 
  // A reference to the accessor of the image.
  const NeighborhoodAccessorFunctorType & m_NeighborhoodAccessor;
 
  // The constant whose value is returned a pixel value outside the image is queried.
  const PixelType m_Constant;
 
 
  // Private helper function. Tells whether the pixel at 'pixelIndex' is inside the image.
  static bool
  IsInside(const IndexType & pixelIndex, const ImageSizeType & imageSize) noexcept
  {
    bool result = true;
 
    for (ImageDimensionType i = 0; i < ImageDimension; ++i)
    {
      const IndexValueType indexValue = pixelIndex[i];
 
      // Note: Do not 'quickly' break or return out of the for-loop when the
      // result is false! For performance reasons (loop unrolling, etc.) it
      // appears preferable to complete the for-loop iteration in this case!
      result = result && (indexValue >= 0) && (static_cast<ImageSizeValueType>(indexValue) < imageSize[i]);
    }
    return result;
  }
 
 
  // Private helper function. Calculates and returns the index value of the
  // current pixel within the image buffer.
  static IndexValueType
  CalculatePixelIndexValue(const OffsetType & offsetTable, const IndexType & pixelIndex) noexcept
  {
    IndexValueType result = 0;
 
    for (ImageDimensionType i = 0; i < ImageDimension; ++i)
    {
      result += pixelIndex[i] * offsetTable[i];
    }
    return result;
  }
 
public:
  using PixelAccessParameterType = PixelType;
 
  // Deleted member functions:
  ConstantBoundaryImageNeighborhoodPixelAccessPolicy() = delete;
  ConstantBoundaryImageNeighborhoodPixelAccessPolicy &
  operator=(const ConstantBoundaryImageNeighborhoodPixelAccessPolicy &) = delete;
 
  // Explicitly-defaulted functions:
  ~ConstantBoundaryImageNeighborhoodPixelAccessPolicy() = default;
  ConstantBoundaryImageNeighborhoodPixelAccessPolicy(const ConstantBoundaryImageNeighborhoodPixelAccessPolicy &) =
    default;
 
  ConstantBoundaryImageNeighborhoodPixelAccessPolicy(const ImageSizeType &                   imageSize,
                                                     const OffsetType &                      offsetTable,
                                                     const NeighborhoodAccessorFunctorType & neighborhoodAccessor,
                                                     const IndexType &                       pixelIndex,
                                                     const PixelType                         constant = {}) noexcept
    : m_PixelIndexValue{ IsInside(pixelIndex, imageSize) ? CalculatePixelIndexValue(offsetTable, pixelIndex) : -1 }
    , m_NeighborhoodAccessor(neighborhoodAccessor)
    , m_Constant{ constant }
  {}
  PixelType
  GetPixelValue(const InternalPixelType * const imageBufferPointer) const noexcept
  {
    return (m_PixelIndexValue < 0) ? m_Constant : m_NeighborhoodAccessor.Get(imageBufferPointer + m_PixelIndexValue);
  }
 
  void
  SetPixelValue(InternalPixelType * const imageBufferPointer, const PixelType & pixelValue) const noexcept
  {
    if (m_PixelIndexValue >= 0)
    {
      m_NeighborhoodAccessor.Set(imageBufferPointer + m_PixelIndexValue, pixelValue);
    }
  }
};
} // namespace itk
 
#endif