#include <itkNeighborhoodIterator.h>

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

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

Detailed Description

template<class TImage, class 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> IP;
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 <<
    IP(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 http://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:

All Examples

Iterate over a region of an image with a neighborhood (with write access)

NeighborhoodIterator on a VectorImage

Examples:: itkVectorImageTest.cxx.

Definition at line 217 of file itkNeighborhoodIterator.h.

Public Types
typedef Superclass::ConstIterator	ConstIterator

typedef Superclass::ImageBoundaryConditionPointerType	ImageBoundaryConditionPointerType

typedef Superclass::ImageType	ImageType

typedef Superclass::IndexType	IndexType

typedef Superclass::InternalPixelType	InternalPixelType

typedef Superclass::Iterator	Iterator

typedef Superclass::NeighborhoodType	NeighborhoodType

typedef Superclass::OffsetType	OffsetType

typedef Superclass::PixelType	PixelType

typedef Superclass::RadiusType	RadiusType

typedef Superclass::RegionType	RegionType

typedef NeighborhoodIterator	Self

typedef Superclass::SizeType	SizeType

typedef ConstNeighborhoodIterator < TImage, TBoundaryCondition >	Superclass

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

typedef Superclass::ConstIterator	ConstIterator

typedef unsigned int	DimensionValueType

typedef ImageBoundaryCondition < ImageType > const *	ImageBoundaryConditionConstPointerType

typedef ImageBoundaryCondition < ImageType > *	ImageBoundaryConditionPointerType

typedef TImage::InternalPixelType	InternalPixelType

typedef Superclass::Iterator	Iterator

typedef ImageType::NeighborhoodAccessorFunctorType	NeighborhoodAccessorFunctorType

typedef NeighborhoodType::NeighborIndexType	NeighborIndexType

typedef Superclass::OffsetType	OffsetType

typedef TImage::PixelType	PixelType

typedef Superclass::RadiusType	RadiusType

typedef ConstNeighborhoodIterator	Self

typedef Superclass::SizeType	SizeType

typedef Neighborhood < InternalPixelType *, itkGetStaticConstMacro(Dimension) >	Superclass

typedef TImage	ImageType

typedef TImage::RegionType	RegionType

typedef Index < itkGetStaticConstMacro(Dimension) >	IndexType

typedef Neighborhood < PixelType, itkGetStaticConstMacro(Dimension) >	NeighborhoodType

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

typedef AllocatorType::const_iterator	ConstIterator

typedef unsigned int	DimensionValueType

typedef AllocatorType::iterator	Iterator

typedef SizeValueType	NeighborIndexType

typedef Offset< VDimension >	OffsetType

typedef TImage::InternalPixelType *	PixelType

typedef Neighborhood	Self

typedef SizeType::SizeValueType	SizeValueType

typedef SliceIterator < TImage::InternalPixelType *, Self >	SliceIteratorType

Public Member Functions
InternalPixelType *	GetCenterPointer ()

	NeighborhoodIterator ()

	NeighborhoodIterator (const NeighborhoodIterator &n)

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

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

virtual void	SetCenterPixel (const PixelType &p)

virtual void	SetNeighborhood (const NeighborhoodType &)

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

virtual void	SetNext (const unsigned axis, const PixelType &v)

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

virtual void	SetPixel (const unsigned i, const PixelType &v)

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


Self &	operator= (const Self &orig)


virtual void	SetPixel (const OffsetType o, const PixelType &v)


virtual void	SetPrevious (const unsigned axis, const PixelType &v)

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

const ImageType *	GetImagePointer (void) const

virtual IndexType	GetIndex (void) const

virtual IndexType	GetIndex (const OffsetType &o) const

virtual IndexType	GetIndex (NeighborIndexType i) const

bool	GetNeedToUseBoundaryCondition () const

virtual NeighborhoodType	GetNeighborhood () const

virtual PixelType	GetNext (const unsigned axis, NeighborIndexType i) const

virtual PixelType	GetNext (const unsigned axis) const

virtual PixelType	GetPixel (NeighborIndexType i, bool &IsInBounds) const

virtual PixelType	GetPixel (const OffsetType &o) const

virtual PixelType	GetPixel (const OffsetType &o, bool &IsInBounds) const

virtual PixelType	GetPrevious (const unsigned axis, NeighborIndexType i) const

virtual PixelType	GetPrevious (const unsigned axis) const

RegionType	GetRegion () const

OffsetType	GetWrapOffset () const

OffsetValueType	GetWrapOffset (NeighborIndexType n) const

virtual void	GoToBegin ()

virtual void	GoToEnd ()

bool	InBounds () const

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

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

virtual bool	IsAtBegin () const

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

virtual void	OverrideBoundaryCondition (const ImageBoundaryConditionPointerType i)

virtual void	ResetBoundaryCondition ()

void	SetBoundaryCondition (const TBoundaryCondition &c)

void	SetNeedToUseBoundaryCondition (bool b)

virtual void	SetRegion (const RegionType &region)

virtual	~ConstNeighborhoodIterator ()

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

virtual PixelType	GetPixel (NeighborIndexType i) const

virtual bool	IsAtEnd () const

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

	Neighborhood (const Self &other)

bool	operator!= (const Self &other) const

Self &	operator= (const Self &other)

bool	operator== (const Self &other) const

void	Print (std::ostream &os) const

void	SetRadius (const SizeType &)

void	SetRadius (const SizeValueType *rad)

void	SetRadius (const SizeValueType)

NeighborIndexType	Size () const

virtual	~Neighborhood ()

	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

AllocatorType &	GetBufferReference ()

const AllocatorType &	GetBufferReference () const

Additional Inherited Members
Public Attributes inherited from itk::Neighborhood< TImage::InternalPixelType *, TImage::ImageDimension >
typedef::itk::Size< VDimension >	RadiusType

typedef::itk::Size< VDimension >	SizeType

Static Public Attributes inherited from itk::ConstNeighborhoodIterator< TImage, TBoundaryCondition >
static const unsigned int	Dimension = TImage::ImageDimension

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

virtual void	SetBound (const SizeType &)

virtual void	SetEndIndex ()

virtual void	SetLoop (const IndexType &p)

virtual void	SetPixelPointers (const IndexType &)

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

bool	m_IsInBoundsValid

IndexType	m_Loop

bool	m_NeedToUseBoundaryCondition

NeighborhoodAccessorFunctorType	m_NeighborhoodAccessorFunctor

RegionType	m_Region

OffsetType	m_WrapOffset