itkShapedImageNeighborhoodRange.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
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 *         https://www.apache.org/licenses/LICENSE-2.0.txt
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 *  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.
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#ifndef itkShapedImageNeighborhoodRange_h
#define itkShapedImageNeighborhoodRange_h
 
#include <algorithm> // For copy_n.
#include <cassert>
#include <cstddef>  // For ptrdiff_t.
#include <iterator> // For random_access_iterator_tag.
#include <limits>
#include <type_traits> // For conditional and is_const.
 
#include "itkIndex.h"
#include "itkSize.h"
#include "itkZeroFluxNeumannImageNeighborhoodPixelAccessPolicy.h"
 
namespace itk
{
 
template <typename TImage,
          typename TImageNeighborhoodPixelAccessPolicy = ZeroFluxNeumannImageNeighborhoodPixelAccessPolicy<TImage>>
class ShapedImageNeighborhoodRange final
{
private:
  // Empty struct, used internally to denote that there is no pixel access parameter specified.
  struct EmptyPixelAccessParameter
  {};
 
 
  // Helper class to estimate whether the policy has nested type PixelAccessParameterType.
  class CheckPolicy
  {
  private:
    // The Test function has two overloads whose return type is different.
    // One of the overloads is only available for overload resolution when
    // the policy T has a nested type PixelAccessParameterType (using SFINAE).
 
    template <typename T>
    static int
    Test(typename T::PixelAccessParameterType *);
 
    template <typename T>
    static void
    Test(...);
 
  public:
    // This constant tells whether the policy has a PixelAccessParameterType:
    static constexpr bool HasPixelAccessParameterType =
      !std::is_same<decltype(Test<TImageNeighborhoodPixelAccessPolicy>(nullptr)),
                    decltype(Test<TImageNeighborhoodPixelAccessPolicy>())>::value;
  };
 
 
  template <typename TPolicy, bool VPolicyHasPixelAccessParameterType = CheckPolicy::HasPixelAccessParameterType>
  struct OptionalPixelAccessParameter
  {
    using Type = typename TPolicy::PixelAccessParameterType;
  };
 
  // Specialization for when the policy does not have PixelAccessParameterType.
  template <typename TPolicy>
  struct OptionalPixelAccessParameter<TPolicy, false>
  {
    using Type = EmptyPixelAccessParameter;
  };
 
 
  using ImageType = TImage;
  using ImageDimensionType = typename TImage::ImageDimensionType;
  using ImageSizeType = typename TImage::SizeType;
  using ImageSizeValueType = typename TImage::SizeValueType;
  using ImageRegionType = typename TImage::RegionType;
  using PixelType = typename TImage::PixelType;
  using InternalPixelType = typename TImage::InternalPixelType;
  using NeighborhoodAccessorFunctorType = typename TImage::NeighborhoodAccessorFunctorType;
  static constexpr ImageDimensionType ImageDimension = TImage::ImageDimension;
  using IndexType = typename TImage::IndexType;
  using IndexValueType = typename TImage::IndexValueType;
  using OffsetType = Offset<ImageDimension>;
  using OptionalPixelAccessParameterType =
    typename OptionalPixelAccessParameter<TImageNeighborhoodPixelAccessPolicy>::Type;
 
 
  // PixelProxy: internal class that aims to act like a reference to a pixel:
  // It acts either like 'PixelType &' or like 'const PixelType &', depending
  // on its boolean template argument, VIsConst.
  // The proxy retrieves the pixel value using a ImageNeighborhoodPixelAccessPolicy.
  // Note: the extra TDummy argument aims to fix AppleClang 6.0.0.6000056 error
  // "explicit specialization of 'PixelProxy'"and GCC 5.4.0 error "explicit
  // specialization in non-namespace scope".
  template <bool VIsConst, typename TDummy = void>
  class PixelProxy
  {};
 
  // PixelProxy specialization for const pixel types:
  // acts like 'const PixelType &'
  template <typename TDummy>
  class PixelProxy<true, TDummy> final
  {
  private:
    // Pointer to the buffer of the image. Should not be null.
    const InternalPixelType * const m_ImageBufferPointer;
 
    // Pixel access policy.
    const TImageNeighborhoodPixelAccessPolicy m_PixelAccessPolicy;
 
  public:
    // Deleted member functions:
    PixelProxy() = delete;
    PixelProxy &
    operator=(const PixelProxy &) = delete;
 
    // Explicitly-defaulted member functions:
    PixelProxy(const PixelProxy &) noexcept = default;
    ~PixelProxy() = default;
 
    // Constructor, called directly by operator*() of the iterator class.
    PixelProxy(const InternalPixelType * const             imageBufferPointer,
               const TImageNeighborhoodPixelAccessPolicy & pixelAccessPolicy) noexcept
      : m_ImageBufferPointer{ imageBufferPointer }
      , m_PixelAccessPolicy{ pixelAccessPolicy }
    {}
 
    // Allows implicit conversion from non-const to const proxy.
    PixelProxy(const PixelProxy<false> & pixelProxy) noexcept
      : m_ImageBufferPointer{ pixelProxy.m_ImageBufferPointer }
      , m_PixelAccessPolicy{ pixelProxy.m_PixelAccessPolicy }
    {}
 
    // Conversion operator.
    operator PixelType() const noexcept { return m_PixelAccessPolicy.GetPixelValue(m_ImageBufferPointer); }
  };
 
 
  // PixelProxy specialization for non-const pixel types:
  // acts like 'PixelType &'.
  template <typename TDummy>
  class PixelProxy<false, TDummy> final
  {
  private:
    // The const proxy is a friend, to ease implementing conversion from
    // a non-const proxy to a const proxy.
    friend class PixelProxy<true>;
 
    // Pointer to the buffer of the image. Should not be null.
    InternalPixelType * const m_ImageBufferPointer;
 
    // Pixel access policy.
    const TImageNeighborhoodPixelAccessPolicy m_PixelAccessPolicy;
 
  public:
    // Deleted member functions:
    PixelProxy() = delete;
 
    // Explicitly-defaulted member functions:
    ~PixelProxy() = default;
    PixelProxy(const PixelProxy &) noexcept = default;
 
    // Constructor, called directly by operator*() of the iterator class.
    PixelProxy(InternalPixelType * const                   imageBufferPointer,
               const TImageNeighborhoodPixelAccessPolicy & pixelAccessPolicy) noexcept
      : m_ImageBufferPointer{ imageBufferPointer }
      , m_PixelAccessPolicy{ pixelAccessPolicy }
    {}
 
    // Conversion operator.
    operator PixelType() const noexcept { return m_PixelAccessPolicy.GetPixelValue(m_ImageBufferPointer); }
 
    // Operator to assign a pixel value to the proxy.
    PixelProxy &
    operator=(const PixelType & pixelValue) noexcept
    {
      m_PixelAccessPolicy.SetPixelValue(m_ImageBufferPointer, pixelValue);
      return *this;
    }
 
    // Copy-assignment operator.
    PixelProxy &
    operator=(const PixelProxy & pixelProxy) noexcept
    {
      // Note that this assignment operator only copies the pixel value.
      // That is the normal behavior when a reference is assigned to another.
      const PixelType pixelValue = pixelProxy;
      *this = pixelValue;
      return *this;
    }
 
 
    friend void
    swap(PixelProxy lhs, PixelProxy rhs) noexcept
    {
      const auto lhsPixelValue = lhs.m_PixelAccessPolicy.GetPixelValue(lhs.m_ImageBufferPointer);
      const auto rhsPixelValue = rhs.m_PixelAccessPolicy.GetPixelValue(rhs.m_ImageBufferPointer);
 
      // Swap only the pixel values, not the image buffer pointers!
      lhs.m_PixelAccessPolicy.SetPixelValue(lhs.m_ImageBufferPointer, rhsPixelValue);
      rhs.m_PixelAccessPolicy.SetPixelValue(rhs.m_ImageBufferPointer, lhsPixelValue);
    }
  };
 
 
  template <bool VIsConst>
  class QualifiedIterator final
  {
  private:
    // Const and non-const iterators are friends, in order to implement the
    // constructor that allow conversion from non-const to const iterator.
    friend class QualifiedIterator<!VIsConst>;
 
    // ShapedImageNeighborhoodRange is a friend, as it should be the only one that can
    // directly use the private constructor of the iterator.
    friend class ShapedImageNeighborhoodRange;
 
    // Image type class that is either 'const' or non-const qualified, depending on QualifiedIterator and TImage.
    using QualifiedImageType = std::conditional_t<VIsConst, const ImageType, ImageType>;
 
    static constexpr bool IsImageTypeConst = std::is_const<QualifiedImageType>::value;
 
    using QualifiedInternalPixelType = std::conditional_t<IsImageTypeConst, const InternalPixelType, InternalPixelType>;
 
    // Pixel type class that is either 'const' or non-const qualified, depending on QualifiedImageType.
    using QualifiedPixelType = std::conditional_t<IsImageTypeConst, const PixelType, PixelType>;
 
    // Pointer to the buffer of the image. Only null when the iterator is default-constructed.
    QualifiedInternalPixelType * m_ImageBufferPointer = nullptr;
 
    // Image size.
    ImageSizeType m_ImageSize = { {} };
 
    // A copy of the offset table of the image.
    OffsetType m_OffsetTable = { {} };
 
    // The accessor of the image.
    NeighborhoodAccessorFunctorType m_NeighborhoodAccessor;
 
    OptionalPixelAccessParameterType m_OptionalPixelAccessParameter;
 
    // The pixel coordinates of the location of the neighborhood, relative to
    // the index of the first pixel of the buffered region. Note that this
    // location does not have to be within buffered region. It may also be
    // outside the image.
    IndexType m_RelativeLocation = { {} };
 
    const OffsetType * m_CurrentOffset = nullptr;
 
    // Private constructor, used to create the begin and the end iterator of a range.
    // Only used by its friend class ShapedImageNeighborhoodRange.
    QualifiedIterator(QualifiedInternalPixelType * const      imageBufferPointer,
                      const ImageSizeType &                   imageSize,
                      const OffsetType &                      offsetTable,
                      const NeighborhoodAccessorFunctorType & neighborhoodAccessor,
                      const OptionalPixelAccessParameterType  optionalPixelAccessParameter,
                      const IndexType &                       relativeLocation,
                      const OffsetType * const                offset) noexcept
      : m_ImageBufferPointer{ imageBufferPointer }
      ,
      // Note: Use parentheses instead of curly braces to initialize data members,
      // to avoid AppleClang 6.0.0.6000056 compilation error, "no viable conversion..."
      m_ImageSize(imageSize)
      , m_OffsetTable(offsetTable)
      , m_NeighborhoodAccessor(neighborhoodAccessor)
      , m_OptionalPixelAccessParameter(optionalPixelAccessParameter)
      , m_RelativeLocation(relativeLocation)
      , m_CurrentOffset{ offset }
    {}
 
 
    TImageNeighborhoodPixelAccessPolicy CreatePixelAccessPolicy(EmptyPixelAccessParameter) const
    {
      return TImageNeighborhoodPixelAccessPolicy{
        m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_RelativeLocation + *m_CurrentOffset
      };
    }
 
    template <typename TPixelAccessParameter>
    TImageNeighborhoodPixelAccessPolicy
    CreatePixelAccessPolicy(const TPixelAccessParameter pixelAccessParameter) const
    {
      static_assert(std::is_same<TPixelAccessParameter, OptionalPixelAccessParameterType>::value,
                    "This helper function should only be used for OptionalPixelAccessParameterType!");
      static_assert(!std::is_same<TPixelAccessParameter, EmptyPixelAccessParameter>::value,
                    "EmptyPixelAccessParameter indicates that there is no pixel access parameter specified!");
      return TImageNeighborhoodPixelAccessPolicy{
        m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_RelativeLocation + *m_CurrentOffset, pixelAccessParameter
      };
    }
 
  public:
    // Types conforming the iterator requirements of the C++ standard library:
    using difference_type = ptrdiff_t;
    using value_type = PixelType;
    using reference = PixelProxy<IsImageTypeConst>;
    using pointer = QualifiedPixelType *;
    using iterator_category = std::random_access_iterator_tag;
 
 
    QualifiedIterator() = default;
 
    QualifiedIterator(const QualifiedIterator<false> & arg) noexcept
      : m_ImageBufferPointer{ arg.m_ImageBufferPointer }
      ,
      // Note: Use parentheses instead of curly braces to initialize data members,
      // to avoid AppleClang 6.0.0.6000056 compilation error, "no viable conversion..."
      m_ImageSize(arg.m_ImageSize)
      , m_OffsetTable(arg.m_OffsetTable)
      , m_NeighborhoodAccessor(arg.m_NeighborhoodAccessor)
      , m_OptionalPixelAccessParameter(arg.m_OptionalPixelAccessParameter)
      , m_RelativeLocation(arg.m_RelativeLocation)
      , m_CurrentOffset{ arg.m_CurrentOffset }
    {}
    reference operator*() const noexcept
    {
      return reference{ m_ImageBufferPointer, CreatePixelAccessPolicy(m_OptionalPixelAccessParameter) };
    }
    QualifiedIterator &
    operator++() noexcept
    {
      assert(m_CurrentOffset != nullptr);
      ++m_CurrentOffset;
      return *this;
    }
    QualifiedIterator
    operator++(int) noexcept
    {
      auto result = *this;
      ++(*this);
      return result;
    }
    QualifiedIterator &
    operator--() noexcept
    {
      assert(m_CurrentOffset != nullptr);
      --m_CurrentOffset;
      return *this;
    }
    QualifiedIterator
    operator--(int) noexcept
    {
      auto result = *this;
      --(*this);
      return result;
    }
    friend bool
    operator==(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      assert(lhs.m_ImageBufferPointer == rhs.m_ImageBufferPointer);
      assert(lhs.m_ImageSize == rhs.m_ImageSize);
      assert(lhs.m_OffsetTable == rhs.m_OffsetTable);
      return lhs.m_CurrentOffset == rhs.m_CurrentOffset;
    }
 
 
    friend bool
    operator!=(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      // Implemented just like the corresponding std::rel_ops operator.
      return !(lhs == rhs);
    }
 
 
    friend bool
    operator<(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      assert(lhs.m_ImageBufferPointer == rhs.m_ImageBufferPointer);
      assert(lhs.m_ImageSize == rhs.m_ImageSize);
      assert(lhs.m_OffsetTable == rhs.m_OffsetTable);
      return lhs.m_CurrentOffset < rhs.m_CurrentOffset;
    }
 
 
    friend bool
    operator>(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      // Implemented just like the corresponding std::rel_ops operator.
      return rhs < lhs;
    }
 
 
    friend bool
    operator<=(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      // Implemented just like the corresponding std::rel_ops operator.
      return !(rhs < lhs);
    }
 
 
    friend bool
    operator>=(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      // Implemented just like the corresponding std::rel_ops operator.
      return !(lhs < rhs);
    }
 
 
    friend QualifiedIterator &
    operator+=(QualifiedIterator & it, const difference_type n) noexcept
    {
      it.m_CurrentOffset += n;
      return it;
    }
    friend QualifiedIterator &
    operator-=(QualifiedIterator & it, const difference_type n) noexcept
    {
      it += (-n);
      return it;
    }
    friend difference_type
    operator-(const QualifiedIterator & lhs, const QualifiedIterator & rhs) noexcept
    {
      assert(lhs.m_ImageBufferPointer == rhs.m_ImageBufferPointer);
      assert(lhs.m_ImageSize == rhs.m_ImageSize);
      assert(lhs.m_OffsetTable == rhs.m_OffsetTable);
      return lhs.m_CurrentOffset - rhs.m_CurrentOffset;
    }
 
 
    friend QualifiedIterator
    operator+(QualifiedIterator it, const difference_type n) noexcept
    {
      return it += n;
    }
 
 
    friend QualifiedIterator
    operator+(const difference_type n, QualifiedIterator it) noexcept
    {
      return it += n;
    }
 
 
    friend QualifiedIterator
    operator-(QualifiedIterator it, const difference_type n) noexcept
    {
      return it += (-n);
    }
 
 
    reference operator[](const difference_type n) const noexcept { return *(*this + n); }
 
 
    QualifiedIterator &
    operator=(const QualifiedIterator &) noexcept = default;
  };
 
  static constexpr bool IsImageTypeConst = std::is_const<TImage>::value;
 
  using QualifiedInternalPixelType = std::conditional_t<IsImageTypeConst, const InternalPixelType, InternalPixelType>;
 
 
  // Just the data from itk::ImageRegion (not the virtual table)
  struct RegionData
  {
    IndexType     m_Index{ {} };
    ImageSizeType m_Size{ {} };
 
    RegionData() noexcept = default;
 
    explicit RegionData(const ImageRegionType & imageRegion)
      : m_Index(imageRegion.GetIndex())
      , m_Size(imageRegion.GetSize())
    {}
  };
 
 
  void
  SubtractIndex(IndexType & index1, const IndexType & index2)
  {
    for (unsigned int i = 0; i < ImageDimension; ++i)
    {
      index1[i] -= index2[i];
    }
  }
 
  // ShapedImageNeighborhoodRange data members (strictly private):
 
  // Pointer to the buffer of the image.
  QualifiedInternalPixelType * m_ImageBufferPointer{ nullptr };
 
  // Index and size of the buffered image region.
  RegionData m_BufferedRegionData{};
 
  // A copy of the offset table of the image.
  OffsetType m_OffsetTable{ {} };
 
  NeighborhoodAccessorFunctorType m_NeighborhoodAccessor{};
 
  // Index (pixel coordinates) of the location of the neighborhood relative
  // to the origin of the image. Typically it is the location of the
  // center pixel of the neighborhood. It may be outside the image boundaries.
  IndexType m_RelativeLocation{ {} };
 
  // The offsets relative to m_RelativeLocation that specify the neighborhood shape.
  const OffsetType * m_ShapeOffsets{ nullptr };
 
  // The number of neighborhood pixels.
  size_t m_NumberOfNeighborhoodPixels{ 0 };
 
  OptionalPixelAccessParameterType m_OptionalPixelAccessParameter{};
 
public:
  using const_iterator = QualifiedIterator<true>;
  using iterator = QualifiedIterator<IsImageTypeConst>;
  using reverse_iterator = std::reverse_iterator<iterator>;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
  ShapedImageNeighborhoodRange() = default;
 
  ShapedImageNeighborhoodRange(ImageType &                            image,
                               const IndexType &                      location,
                               const OffsetType * const               shapeOffsets,
                               const size_t                           numberOfNeigborhoodPixels,
                               const OptionalPixelAccessParameterType optionalPixelAccessParameter = {})
    : m_ImageBufferPointer{ image.ImageType::GetBufferPointer() }
    ,
    // Note: Use parentheses instead of curly braces to initialize data members,
    // to avoid AppleClang 6.0.0.6000056 compile errors, "no viable conversion..."
    // and "excess elements in struct initializer".
    m_BufferedRegionData(image.ImageType::GetBufferedRegion())
    , m_NeighborhoodAccessor(image.GetNeighborhoodAccessor())
    , m_RelativeLocation(location)
    , m_ShapeOffsets{ shapeOffsets }
    , m_NumberOfNeighborhoodPixels{ numberOfNeigborhoodPixels }
    , m_OptionalPixelAccessParameter(optionalPixelAccessParameter)
  {
    const OffsetValueType * const offsetTable = image.GetOffsetTable();
    assert(offsetTable != nullptr);
    std::copy_n(offsetTable, ImageDimension, m_OffsetTable.begin());
 
    SubtractIndex(m_RelativeLocation, m_BufferedRegionData.m_Index);
    m_NeighborhoodAccessor.SetBegin(m_ImageBufferPointer);
  }
 
  template <typename TContainerOfOffsets>
  ShapedImageNeighborhoodRange(ImageType &                            image,
                               const IndexType &                      location,
                               const TContainerOfOffsets &            shapeOffsets,
                               const OptionalPixelAccessParameterType optionalPixelAccessParameter = {})
    : ShapedImageNeighborhoodRange{ image,
                                    location,
                                    shapeOffsets.data(),
                                    shapeOffsets.size(),
                                    optionalPixelAccessParameter }
  {}
  iterator
  begin() const noexcept
  {
    return iterator{ m_ImageBufferPointer,           m_BufferedRegionData.m_Size, m_OffsetTable, m_NeighborhoodAccessor,
                     m_OptionalPixelAccessParameter, m_RelativeLocation,          m_ShapeOffsets };
  }
 
  iterator
  end() const noexcept
  {
    return iterator{ m_ImageBufferPointer,
                     m_BufferedRegionData.m_Size,
                     m_OffsetTable,
                     m_NeighborhoodAccessor,
                     m_OptionalPixelAccessParameter,
                     m_RelativeLocation,
                     m_ShapeOffsets + m_NumberOfNeighborhoodPixels };
  }
 
  const_iterator
  cbegin() const noexcept
  {
    return this->begin();
  }
 
  const_iterator
  cend() const noexcept
  {
    return this->end();
  }
 
  reverse_iterator
  rbegin() const noexcept
  {
    return reverse_iterator(this->end());
  }
 
  reverse_iterator
  rend() const noexcept
  {
    return reverse_iterator(this->begin());
  }
 
  const_reverse_iterator
  crbegin() const noexcept
  {
    return this->rbegin();
  }
 
  const_reverse_iterator
  crend() const noexcept
  {
    return this->rend();
  }
 
 
  size_t
  size() const noexcept
  {
    return m_NumberOfNeighborhoodPixels;
  }
 
 
  bool
  empty() const noexcept
  {
    return m_NumberOfNeighborhoodPixels == 0;
  }
 
 
  typename QualifiedIterator<false>::reference operator[](const size_t n) const noexcept
  {
    assert(n < this->size());
    assert(n <= static_cast<size_t>(std::numeric_limits<ptrdiff_t>::max()));
    return this->begin()[static_cast<ptrdiff_t>(n)];
  }
 
 
  void
  SetLocation(const IndexType & location) noexcept
  {
    m_RelativeLocation = location;
    SubtractIndex(m_RelativeLocation, m_BufferedRegionData.m_Index);
  }
};
} // namespace itk
 
#endif