itkImageConstIterator.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 itkImageConstIterator_h
#define itkImageConstIterator_h
 
#include "itkImage.h"
#include "itkIndex.h"
#include "itkNumericTraits.h"
 
namespace itk
{
template <typename TImage>
class ITK_TEMPLATE_EXPORT ImageConstIterator
{
public:
  using Self = ImageConstIterator;

  static constexpr unsigned int ImageIteratorDimension = TImage::ImageDimension;

  itkVirtualGetNameOfClassMacro(ImageConstIterator);

  using IndexType = typename TImage::IndexType;

  using SizeType = typename TImage::SizeType;

  using OffsetType = typename TImage::OffsetType;

  using RegionType = typename TImage::RegionType;

  using ImageType = TImage;

  using PixelContainer = typename TImage::PixelContainer;
  using PixelContainerPointer = typename PixelContainer::Pointer;

  using InternalPixelType = typename TImage::InternalPixelType;

  using PixelType = typename TImage::PixelType;

  using AccessorType = typename TImage::AccessorType;
  using AccessorFunctorType = typename TImage::AccessorFunctorType;

  ImageConstIterator()
    : m_Region()
    , m_PixelAccessor()
    , m_PixelAccessorFunctor()
  {
    m_Image = nullptr;
    m_Buffer = nullptr;
    m_Offset = 0;
    m_BeginOffset = 0;
    m_EndOffset = 0;
    m_PixelAccessorFunctor.SetBegin(m_Buffer);
  }


  virtual ~ImageConstIterator() = default;

  ImageConstIterator(const Self & it)
  {
    m_Image = it.m_Image; // copy the smart pointer
 
    m_Region = it.m_Region;
 
    m_Buffer = it.m_Buffer;
    m_Offset = it.m_Offset;
    m_BeginOffset = it.m_BeginOffset;
    m_EndOffset = it.m_EndOffset;
    m_PixelAccessor = it.m_PixelAccessor;
    m_PixelAccessorFunctor = it.m_PixelAccessorFunctor;
    m_PixelAccessorFunctor.SetBegin(m_Buffer);
  }

  ImageConstIterator(const ImageType * ptr, const RegionType & region)
  {
    m_Image = ptr;
    m_Buffer = m_Image->GetBufferPointer();
 
    SetRegion(region);
 
    m_PixelAccessor = ptr->GetPixelAccessor();
    m_PixelAccessorFunctor.SetPixelAccessor(m_PixelAccessor);
    m_PixelAccessorFunctor.SetBegin(m_Buffer);
  }

  Self &
  operator=(const Self & it)
  {
    if (this != &it)
    {
      m_Image = it.m_Image; // copy the smart pointer
      m_Region = it.m_Region;
 
      m_Buffer = it.m_Buffer;
      m_Offset = it.m_Offset;
      m_BeginOffset = it.m_BeginOffset;
      m_EndOffset = it.m_EndOffset;
      m_PixelAccessor = it.m_PixelAccessor;
      m_PixelAccessorFunctor = it.m_PixelAccessorFunctor;
      m_PixelAccessorFunctor.SetBegin(m_Buffer);
    }
    return *this;
  }

  virtual void
  SetRegion(const RegionType & region)
  {
    m_Region = region;
 
    if (region.GetNumberOfPixels() > 0) // If region is non-empty
    {
      const RegionType & bufferedRegion = m_Image->GetBufferedRegion();
      itkAssertOrThrowMacro((bufferedRegion.IsInside(m_Region)),
                            "Region " << m_Region << " is outside of buffered region " << bufferedRegion);
    }
 
    // Compute the start offset
    m_Offset = m_Image->ComputeOffset(m_Region.GetIndex());
    m_BeginOffset = m_Offset;
 
    // Compute the end offset. If any component of m_Region.GetSize()
    // is zero, the region is not valid and we set the EndOffset
    // to be same as BeginOffset so that iterator end condition is met
    // immediately.
    IndexType ind(m_Region.GetIndex());
    SizeType  size(m_Region.GetSize());
    if (m_Region.GetNumberOfPixels() == 0)
    {
      // region is empty, probably has a size of 0 along one dimension
      m_EndOffset = m_BeginOffset;
    }
    else
    {
      for (unsigned int i = 0; i < TImage::ImageDimension; ++i)
      {
        ind[i] += (static_cast<IndexValueType>(size[i]) - 1);
      }
      m_EndOffset = m_Image->ComputeOffset(ind);
      ++m_EndOffset;
    }
  }

  static unsigned int
  GetImageIteratorDimension()
  {
    return TImage::ImageDimension;
  }

  bool
  operator==(const Self & it) const
  {
    // two iterators are the same if they "point to" the same memory location
    return (m_Buffer + m_Offset) == (it.m_Buffer + it.m_Offset);
  }
 
  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Self);

  bool
  operator<=(const Self & it) const
  {
    // an iterator is "less than" another if it "points to" a lower
    // memory location
    return (m_Buffer + m_Offset) <= (it.m_Buffer + it.m_Offset);
  }

  bool
  operator<(const Self & it) const
  {
    // an iterator is "less than" another if it "points to" a lower
    // memory location
    return (m_Buffer + m_Offset) < (it.m_Buffer + it.m_Offset);
  }

  bool
  operator>=(const Self & it) const
  {
    // an iterator is "greater than" another if it "points to" a higher
    // memory location
    return (m_Buffer + m_Offset) >= (it.m_Buffer + it.m_Offset);
  }

  bool
  operator>(const Self & it) const
  {
    // an iterator is "greater than" another if it "points to" a higher
    // memory location
    return (m_Buffer + m_Offset) > (it.m_Buffer + it.m_Offset);
  }

  const IndexType
  GetIndex() const
  {
    return m_Image->ComputeIndex(static_cast<OffsetValueType>(m_Offset));
  }

  virtual void
  SetIndex(const IndexType & ind)
  {
    m_Offset = m_Image->ComputeOffset(ind);
  }

  const RegionType &
  GetRegion() const
  {
    return m_Region;
  }

  const ImageType *
  GetImage() const
  {
    return m_Image.GetPointer();
  }

  PixelType
  Get() const
  {
    return m_PixelAccessorFunctor.Get(*(m_Buffer + m_Offset));
  }

  const PixelType &
  Value() const
  {
    return *(m_Buffer + m_Offset);
  }

  void
  GoToBegin()
  {
    m_Offset = m_BeginOffset;
  }

  void
  GoToEnd()
  {
    m_Offset = m_EndOffset;
  }

  bool
  IsAtBegin() const
  {
    return (m_Offset == m_BeginOffset);
  }

  bool
  IsAtEnd() const
  {
    return (m_Offset == m_EndOffset);
  }
 
protected: // made protected so other iterators can access
  typename TImage::ConstWeakPointer m_Image{};
 
  RegionType m_Region{}; // region to iterate over
 
  OffsetValueType m_Offset{};
  OffsetValueType m_BeginOffset{}; // offset to first pixel in region
  OffsetValueType m_EndOffset{};   // offset to one pixel past last pixel in region
 
  const InternalPixelType * m_Buffer{};
 
  AccessorType        m_PixelAccessor{};
  AccessorFunctorType m_PixelAccessorFunctor{};
};
} // end namespace itk
 
#endif