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itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition > Class Template Reference
[Image Iterators]

#include <itkShapedNeighborhoodIterator.h>

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

[legend]Collaboration diagram for itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >:

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Detailed Description

template<class TImage, class TBoundaryCondition = ZeroFluxNeumannBoundaryCondition<TImage>>
class itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >

A neighborhood iterator which can take on an arbitrary shape.

General Information: The ShapedNeighborhoodIterator is a refinement of NeighborhoodIterator which allows the user to specify which of the neighborhood elements are active and which will be ignored. This is useful for applications which only need to work with a subset of the neighborhood around a pixel such as morphological operations or cellular automata. This iterator can also be used, for example, to specify "cross-shaped" neighborhood where only elements along a spatial axes are significant.

Constructing a shaped neighborhood iterator: A shaped neighborhood iterator is constructed by constructing a list of active neighbor locations. The list is called the ActiveIndexList. The methods ActivateOffset, DeactivateOffset, and ClearActiveList are used to construct the ActiveIndexList. The argument to Activate/DeactivateOffset is an itk::Offset which represents the ND spatial offset from the center of the neighborhood. For example, to activate the center pixel in the neighborhood, you would do the following:

 typedef Image<float, 3> ImageType;
 ShapedNeighborhoodIterator<ImageType> it(radius, image, region);
 ShapedNeighborhoodIterator<ImageType>::OffsetType offset = {{0,0,0}};
 it.ActivateOffset(offset);

where radius, image, and region are as described in NeighborhoodIterator.

Once a neighborhood location has been activated, iteration (operator++, operator--, operator+=, operator-=) will update the value at the active location. Note that values at inactive locations will NOT be valid if queried.

Accessing elements in a shaped neighborhood.: To access the value at an active neighborhood location, you can use the standard GetPixel, SetPixel methods. SetPixel is not defined for ConstShapedNeighborhoodIterator. The class will not complain if you attempt to access a value at a non-active location, but be aware that the result will be undefined. Error checking is not done in this case for the sake of efficiency.

A second way to access active shaped neighborhood values is through a ShapedNeighborhoodIterator::Iterator or ConstShapedNeighborhoodIterator::ConstIterator. The following example demonstrates the use of these iterators.

 typedef Image<float, 3> ImageType;
 ShapedNeighborhoodIterator<ImageType> it(radius, image, region);
 .
 .
 .
 it.ActivateOffset(offset1);
 it.ActivateOffset(offset2);
 it.ActivateOffset(offset3);
 etc..
 .
 .
 .
 ShapedNeighborhoodIterator<ImageType>::Iterator i;
 for (i = it.Begin(); ! i.IsAtEnd(); i++)
 { i.Set(i.Get() + 1.0); }
 \\ you may also use i != i.End(), but IsAtEnd() may be slightly faster.

You can also iterate backward through the neighbohood active list.

 i = it.End();
 i--;
 while (i != it.Begin())
 {
   i.Set(i.Get() + 1.0);
   i--;
 }
  i.Set(i.Get() + 1.0);

The Get() Set() syntax was chosen versus defining operator* for these iterators because lvalue vs. rvalue context information is needed to determine whether bounds checking must take place.

See also:: Neighborhood

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

Examples:: Testing/Code/Common/itkVectorImageTest.cxx.