itkImageConstIterator.h

Go to the documentation of this file.

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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;

  itkTypeMacroNoParent(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 );
  }

  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 );
  }

  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