#include <itkNeighborhoodIterator.h>

Inheritance diagram for itk::NeighborhoodIterator< TImage, TBoundaryCondition >:

Collaboration diagram for itk::NeighborhoodIterator< TImage, TBoundaryCondition >:

Detailed Description

template<typename TImage, typename TBoundaryCondition = ZeroFluxNeumannBoundaryCondition< TImage >>
class itk::NeighborhoodIterator< TImage, TBoundaryCondition >

Defines iteration of a local N-dimensional neighborhood of pixels across an itk::Image.

This class is a loose extension of the Standard Template Library (STL) bi-directional iterator concept to masks of pixel neighborhoods within itk::Image objects. This NeighborhoodIterator base class defines simple forward and reverse iteration of an N-dimensional neighborhood mask across an image. Elements within the mask can be accessed like elements within an array.

NeighborhoodIterators are designed to encapsulate some of the complexity of working with image neighborhoods, complexity that would otherwise have to be managed at the algorithmic level. Use NeighborhoodIterators to simplify writing algorithms that perform geometrically localized operations on images (for example, convolution and morphological operations).

To motivate the discussion of NeighborhoodIterators and their use in Itk, consider the following code that takes directional derivatives at each point in an image.

itk::NeighborhoodInnerProduct<ImageType> innerProduct;
itk::DerivativeOperator<ImageType> operator;
 operator->SetOrder(1);
 operator->SetDirection(0);
 operator->CreateDirectional();
itk::NeighborhoodIterator<ImageType>
  iterator(operator->GetRadius(), myImage, myImage->GetRequestedRegion());
iterator.SetToBegin();
while ( ! iterator.IsAtEnd() )
{
  std::cout << "Derivative at index " << iterator.GetIndex() << is <<
    innerProduct(iterator, operator) << std::endl;
  ++iterator;
}

Most of the work for the programmer in the code above is in setting up for the iteration. There are three steps. First an inner product function object is created which will be used to effect convolution with the derivative kernel. Setting up the derivative kernel, DerivativeOperator, involves setting the order and direction of the derivative. Finally, we create an iterator over the RequestedRegion of the itk::Image (see Image) using the radius of the derivative kernel as the size.

Itk iterators only loosely follow STL conventions. Notice that instead of asking myImage for myImage.begin() and myImage.end(), iterator.SetToBegin() and iterator.IsAtEnd() are called. Itk iterators are typically more complex objects than traditional, pointer-style STL iterators, and the increased overhead required to conform to the complete STL API is not always justified.

The API for creating and manipulating a NeighborhoodIterator mimics that of the itk::ImageIterators. Like the itk::ImageIterator, a ConstNeighborhoodIterator is defined on a region of interest in an itk::Image. Iteration is constrained within that region of interest.

A NeighborhoodIterator is constructed as a container of pointers (offsets) to a geometric neighborhood of image pixels. As the central pixel position in the mask is moved around the image, the neighboring pixel pointers (offsets) are moved accordingly.

A pixel neighborhood is defined as a central pixel location and an N-dimensional radius extending outward from that location.

Pixels in a neighborhood can be accessed through a NeighborhoodIterator like elements in an array. For example, a 2D neighborhood with radius 2x1 has indices:

1  2  3  4
6  7  8  9
11 12 13 14

Now suppose a NeighborhoodIterator with the above dimensions is constructed and positioned over a neighborhood of values in an Image:

2 1.3 1.8 1.4 1.1
8 1.1 0.7 1.0 1.0
1 1.9 1.7 1.4 2.0

Shown below is some sample pixel access code and the values that it returns.

SizeValueType c = (SizeValueType) (iterator.Size() / 2); // get offset of center pixel
SizeValueType s = iterator.GetStride(1);            // y-dimension step size
std::cout << iterator.GetPixel(7)      << std::endl;
std::cout << iterator.GetCenterPixel() << std::endl;
std::cout << iterator.GetPixel(c)      << std::endl;
std::cout << iterator.GetPixel(c-1)    << std::endl;
std::cout << iterator.GetPixel(c-s)    << std::endl;
std::cout << iterator.GetPixel(c-s-1)  << std::endl;
std::cout << *iterator[c]              << std::endl;

Results:

Use of GetPixel() is preferred over the *iterator[] form, and can be used without loss of efficiency in most cases. Some variations (subclasses) of NeighborhoodIterators may exist which do not support the latter API. Corresponding SetPixel() methods exist to modify pixel values in non-const NeighborhoodIterators.

NeighborhoodIterators are "bidirectional iterators". They move only in two directions through the data set. These directions correspond to the layout of the image data in memory and not to spatial directions of the N-dimensional itk::Image. Iteration always proceeds along the fastest increasing dimension (as defined by the layout of the image data). For itk::Image this is the first dimension specified (i.e. for 3-dimensional (x,y,z) NeighborhoodIterator proceeds along the x-dimension) (For random access iteration through N-dimensional indices, use RandomAccessNeighborhoodIterator).

Each subclass of a ConstNeighborhoodIterator may also define its own mechanism for iteration through an image. In general, the Iterator does not directly keep track of its spatial location in the image, but uses a set of internal loop variables and offsets to trigger wraps at itk::Image region boundaries, and to identify the end of the itk::Image region.

Todo:

Better support for regions with negative indices.

Add Begin() and End() methods?

See Also: DerivativeOperator; NeighborhoodInnerProduct

MORE INFORMATION: For a complete description of the ITK Image Iterators and their API, please see the Iterators chapter in the ITK Software Guide. The ITK Software Guide is available in print and as a free .pdf download from https://www.itk.org.

See Also: ImageConstIterator; ConditionalConstIterator; ConstNeighborhoodIterator; ConstShapedNeighborhoodIterator; ConstSliceIterator; CorrespondenceDataStructureIterator; FloodFilledFunctionConditionalConstIterator; FloodFilledImageFunctionConditionalConstIterator; FloodFilledImageFunctionConditionalIterator; FloodFilledSpatialFunctionConditionalConstIterator; FloodFilledSpatialFunctionConditionalIterator; ImageConstIterator; ImageConstIteratorWithIndex; ImageIterator; ImageIteratorWithIndex; ImageLinearConstIteratorWithIndex; ImageLinearIteratorWithIndex; ImageRandomConstIteratorWithIndex; ImageRandomIteratorWithIndex; ImageRegionConstIterator; ImageRegionConstIteratorWithIndex; ImageRegionExclusionConstIteratorWithIndex; ImageRegionExclusionIteratorWithIndex; ImageRegionIterator; ImageRegionIteratorWithIndex; ImageRegionReverseConstIterator; ImageRegionReverseIterator; ImageReverseConstIterator; ImageReverseIterator; ImageSliceConstIteratorWithIndex; ImageSliceIteratorWithIndex; NeighborhoodIterator; PathConstIterator; PathIterator; ShapedNeighborhoodIterator; SliceIterator; ImageConstIteratorWithIndex

Wiki Examples:

Examples:: Examples/Iterators/NeighborhoodIterators6.cxx, WikiExamples/Iterators/NeighborhoodIterator.cxx, and WikiExamples/VectorImages/VectorNeighborhoodIterator.cxx.

Definition at line 212 of file itkNeighborhoodIterator.h.

Public Types
using	ConstIterator = typename Superclass::ConstIterator

using	ImageBoundaryConditionPointerType = typename Superclass::ImageBoundaryConditionPointerType

using	ImageType = typename Superclass::ImageType

using	IndexType = typename Superclass::IndexType

using	InternalPixelType = typename Superclass::InternalPixelType

using	Iterator = typename Superclass::Iterator

using	NeighborhoodType = typename Superclass::NeighborhoodType

using	OffsetType = typename Superclass::OffsetType

using	PixelType = typename Superclass::PixelType

using	RadiusType = typename Superclass::RadiusType

using	RegionType = typename Superclass::RegionType

using	Self = NeighborhoodIterator

using	SizeType = typename Superclass::SizeType

using	Superclass = ConstNeighborhoodIterator< TImage, TBoundaryCondition >

Public Types inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
using	BoundaryConditionType = TBoundaryCondition

using	ConstIterator = typename Superclass::ConstIterator

using	DimensionValueType = unsigned int

using	ImageBoundaryConditionConstPointerType = const ImageBoundaryCondition< ImageType, OutputImageType > *

using	ImageBoundaryConditionPointerType = ImageBoundaryCondition< ImageType, OutputImageType > *

using	ImageType = TImage

using	IndexType = Index< Self::Dimension >

using	InternalPixelType = typename TImage::InternalPixelType

using	Iterator = typename Superclass::Iterator

using	NeighborhoodAccessorFunctorType = typename ImageType::NeighborhoodAccessorFunctorType

using	NeighborhoodType = Neighborhood< PixelType, Self::Dimension >

using	NeighborIndexType = typename NeighborhoodType::NeighborIndexType

using	OffsetType = typename Superclass::OffsetType

using	OutputImageType = typename BoundaryConditionType::OutputImageType

using	PixelType = typename TImage::PixelType

using	RadiusType = typename Superclass::RadiusType

using	RegionType = typename TImage::RegionType

using	Self = ConstNeighborhoodIterator

using	SizeType = typename Superclass::SizeType

using	Superclass = Neighborhood< InternalPixelType *, Self::Dimension >

Public Types inherited from itk::Neighborhood< TImage::InternalPixelType *, TImage::ImageDimension >
using	AllocatorType = NeighborhoodAllocator< TImage::InternalPixelType * >

using	ConstIterator = typename AllocatorType::const_iterator

using	DimensionValueType = unsigned int

using	Iterator = typename AllocatorType::iterator

using	NeighborIndexType = SizeValueType

using	OffsetType = Offset< VDimension >

using	PixelType = TImage::InternalPixelType *

using	RadiusType = ::itk::Size< VDimension >

using	Self = Neighborhood

using	SizeType = ::itk::Size< VDimension >

using	SizeValueType = typename SizeType::SizeValueType

using	SliceIteratorType = SliceIterator< TImage::InternalPixelType *, Self >

Public Member Functions
InternalPixelType *	GetCenterPointer ()

	NeighborhoodIterator ()

	NeighborhoodIterator (const NeighborhoodIterator &n)

	NeighborhoodIterator (const SizeType &radius, ImageType *ptr, const RegionType &region)

void	PrintSelf (std::ostream &, Indent) const

ITK_ITERATOR_VIRTUAL void	SetCenterPixel (const PixelType &p) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetNeighborhood (const NeighborhoodType &) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetNext (const unsigned axis, const unsigned i, const PixelType &v) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetNext (const unsigned axis, const PixelType &v) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetPixel (const unsigned i, const PixelType &v, bool &status) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetPixel (const unsigned i, const PixelType &v) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetPrevious (const unsigned axis, const unsigned i, const PixelType &v) ITK_ITERATOR_FINAL


Self &	operator= (const Self &orig)


ITK_ITERATOR_VIRTUAL void	SetPixel (const OffsetType o, const PixelType &v) ITK_ITERATOR_FINAL


ITK_ITERATOR_VIRTUAL void	SetPrevious (const unsigned axis, const PixelType &v) ITK_ITERATOR_FINAL

Public Member Functions inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
OffsetType	ComputeInternalIndex (const NeighborIndexType n) const

	ConstNeighborhoodIterator ()

	ConstNeighborhoodIterator (const ConstNeighborhoodIterator &)

IndexType	GetBeginIndex () const

IndexType	GetBound () const

IndexValueType	GetBound (NeighborIndexType n) const

ImageBoundaryConditionPointerType	GetBoundaryCondition () const

RegionType	GetBoundingBoxAsImageRegion () const

PixelType	GetCenterPixel () const

const InternalPixelType *	GetCenterPointer () const

IndexType	GetFastIndexPlusOffset (const OffsetType &o) const

const ImageType *	GetImagePointer () const

ITK_ITERATOR_VIRTUAL IndexType	GetIndex () const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL IndexType	GetIndex (const OffsetType &o) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL IndexType	GetIndex (NeighborIndexType i) const ITK_ITERATOR_FINAL

bool	GetNeedToUseBoundaryCondition () const

ITK_ITERATOR_VIRTUAL NeighborhoodType	GetNeighborhood () const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetNext (const unsigned axis, NeighborIndexType i) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetNext (const unsigned axis) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPixel (const NeighborIndexType i) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPixel (NeighborIndexType i, bool &IsInBounds) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPixel (const OffsetType &o) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPixel (const OffsetType &o, bool &IsInBounds) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPrevious (const unsigned axis, NeighborIndexType i) const ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL PixelType	GetPrevious (const unsigned axis) const ITK_ITERATOR_FINAL

RegionType	GetRegion () const

OffsetType	GetWrapOffset () const

OffsetValueType	GetWrapOffset (NeighborIndexType n) const

ITK_ITERATOR_VIRTUAL void	GoToBegin () ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	GoToEnd () ITK_ITERATOR_FINAL

bool	InBounds () const

bool	IndexInBounds (const NeighborIndexType n, OffsetType &internalIndex, OffsetType &offset) const

bool	IndexInBounds (const NeighborIndexType n) const

ITK_ITERATOR_VIRTUAL void	Initialize (const SizeType &radius, const ImageType *ptr, const RegionType &region) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL bool	IsAtBegin () const ITK_ITERATOR_FINAL

void	NeedToUseBoundaryConditionOff ()

void	NeedToUseBoundaryConditionOn ()

bool	operator!= (const Self &it) const

Self &	operator++ ()

Self &	operator+= (const OffsetType &)

OffsetType	operator- (const Self &b)

Self &	operator-- ()

Self &	operator-= (const OffsetType &)

bool	operator< (const Self &it) const

bool	operator<= (const Self &it) const

Self &	operator= (const Self &orig)

bool	operator== (const Self &it) const

bool	operator> (const Self &it) const

bool	operator>= (const Self &it) const

ITK_ITERATOR_VIRTUAL void	OverrideBoundaryCondition (const ImageBoundaryConditionPointerType i) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	ResetBoundaryCondition () ITK_ITERATOR_FINAL

void	SetBoundaryCondition (const TBoundaryCondition &c)

void	SetNeedToUseBoundaryCondition (bool b)

ITK_ITERATOR_VIRTUAL void	SetRegion (const RegionType &region) ITK_ITERATOR_FINAL

	~ConstNeighborhoodIterator () override=default

	ConstNeighborhoodIterator (const SizeType &radius, const ImageType *ptr, const RegionType &region)

ITK_ITERATOR_VIRTUAL bool	IsAtEnd () const ITK_ITERATOR_FINAL

void	SetLocation (const IndexType &position)

Public Member Functions inherited from itk::Neighborhood< TImage::InternalPixelType *, TImage::ImageDimension >
NeighborIndexType	GetCenterNeighborhoodIndex () const

TImage::InternalPixelType *	GetCenterValue () const

virtual NeighborIndexType	GetNeighborhoodIndex (const OffsetType &) const

OffsetType	GetOffset (NeighborIndexType i) const

const SizeType	GetRadius () const

SizeValueType	GetRadius (DimensionValueType n) const

SizeValueType	GetSize (DimensionValueType n) const

SizeType	GetSize () const

std::slice	GetSlice (unsigned int) const

OffsetValueType	GetStride (DimensionValueType axis) const

	itkTypeMacroNoParent (Neighborhood)

	Neighborhood (const Self &other)

	Neighborhood (Self &&)=default

bool	operator!= (const Self &other) const

Self &	operator= (const Self &other)

Self &	operator= (Self &&)=default

bool	operator== (const Self &other) const

void	Print (std::ostream &os) const

void	SetRadius (const SizeType &)

void	SetRadius (const SizeValueType)

NeighborIndexType	Size () const

virtual	~Neighborhood ()=default

	Neighborhood ()

Iterator	End ()

ConstIterator	End () const

Iterator	Begin ()

ConstIterator	Begin () const

TImage::InternalPixelType *&	operator[] (NeighborIndexType i)

const TImage::InternalPixelType *&	operator[] (NeighborIndexType i) const

TImage::InternalPixelType *&	GetElement (NeighborIndexType i)

TImage::InternalPixelType *&	operator[] (const OffsetType &o)

const TImage::InternalPixelType *&	operator[] (const OffsetType &o) const

void	SetRadius (const SizeValueType *rad)

AllocatorType &	GetBufferReference ()

const AllocatorType &	GetBufferReference () const

Additional Inherited Members
Static Public Attributes inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
static constexpr DimensionValueType	Dimension = TImage::ImageDimension

Static Public Attributes inherited from itk::Neighborhood< TImage::InternalPixelType *, TImage::ImageDimension >
static constexpr unsigned int	NeighborhoodDimension

Protected Member Functions inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
ITK_ITERATOR_VIRTUAL void	SetBeginIndex (const IndexType &start) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetBound (const SizeType &) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetEndIndex () ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetLoop (const IndexType &p) ITK_ITERATOR_FINAL

ITK_ITERATOR_VIRTUAL void	SetPixelPointers (const IndexType &) ITK_ITERATOR_FINAL

Protected Member Functions inherited from itk::Neighborhood< TImage::InternalPixelType *, TImage::ImageDimension >
virtual void	Allocate (NeighborIndexType i)

virtual void	ComputeNeighborhoodOffsetTable ()

virtual void	ComputeNeighborhoodStrideTable ()

void	SetSize ()

Protected Attributes inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
const InternalPixelType *	m_Begin

IndexType	m_BeginIndex

IndexType	m_Bound

ImageBoundaryConditionPointerType	m_BoundaryCondition

ImageType::ConstWeakPointer	m_ConstImage

const InternalPixelType *	m_End

IndexType	m_EndIndex

bool	m_InBounds [Dimension]

IndexType	m_InnerBoundsHigh

IndexType	m_InnerBoundsLow

TBoundaryCondition	m_InternalBoundaryCondition

bool	m_IsInBounds {false}

bool	m_IsInBoundsValid {false}

IndexType	m_Loop

bool	m_NeedToUseBoundaryCondition {false}

NeighborhoodAccessorFunctorType	m_NeighborhoodAccessorFunctor

RegionType	m_Region

OffsetType	m_WrapOffset