#include <itkNeighborhoodIterator.h>
Inheritance diagram for itk::NeighborhoodIterator< TImage, TBoundaryCondition >:
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:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Now suppose a NeighborhoodIterator with the above dimensions is constructed and positioned over a neighborhood of values in an Image:
1.2 1.3 1.8 1.4 1.1 1.8 1.1 0.7 1.0 1.0 2.1 1.9 1.7 1.4 2.0
Shown below is some sample pixel access code and the values that it returns.
::size_t c = (::size_t) (iterator.Size() / 2); // get offset of center pixel ::size_t 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:
0.7 0.7 0.7 1.1 1.8 1.3 0.7
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 indicies, 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.
Add Begin() and End() methods?
SmartNeighborhoodIterator
RandomAccessNeighborhoodIterator
Definition at line 188 of file itkNeighborhoodIterator.h.
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 208 of file itkNeighborhoodIterator.h. |
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Typedef for generic boundary condition pointer Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 210 of file itkNeighborhoodIterator.h. |
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Typedef support for common objects Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 200 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 202 of file itkNeighborhoodIterator.h. |
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Extract typedefs from superclass. Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 197 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >. Definition at line 207 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 206 of file itkNeighborhoodIterator.h. Referenced by itk::NeighborhoodIterator< TImage, TBoundaryCondition >::SetCenterPixel(). |
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Inherit typedefs from superclass Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 203 of file itkNeighborhoodIterator.h. Referenced by itk::NeighborhoodIterator< TImage, TBoundaryCondition >::SetCenterPixel(). |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 204 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 205 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 201 of file itkNeighborhoodIterator.h. |
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Standard class typedefs. Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 193 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 199 of file itkNeighborhoodIterator.h. |
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Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 194 of file itkNeighborhoodIterator.h. Referenced by itk::NeighborhoodIterator< TImage, TBoundaryCondition >::NeighborhoodIterator(). |
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Default constructor. Definition at line 213 of file itkNeighborhoodIterator.h. |
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Copy constructor Definition at line 216 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::Superclass. |
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Constructor which establishes the region size, neighborhood, and image over which to walk. Definition at line 229 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::Superclass. |
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Returns the central memory pointer of the neighborhood. Definition at line 237 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::PixelType. |
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Assignment operator Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >. Definition at line 220 of file itkNeighborhoodIterator.h. |
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Standard print method Reimplemented from itk::ConstNeighborhoodIterator< TImage >.
Reimplemented in itk::ConstShapedNeighborhoodIterator< TImage, TBoundaryCondition >, and itk::ShapedNeighborhoodIterator< TImage, TBoundaryCondition >.
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Returns the central pixel of the neighborhood. Definition at line 241 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::NeighborhoodType, itk::NeighborhoodIterator< TImage, TBoundaryCondition >::OffsetType, and itk::NeighborhoodIterator< TImage, TBoundaryCondition >::PixelType. |
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Virtual function that replaces the pixel values in the image neighborhood that are pointed to by this NeighborhoodIterator with the pixel values contained in a Neighborhood. |
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Sets the pixel value located one pixel distant from the neighborhood center in the specifed positive axis direction. No bounds checking is done on the size of the neighborhood. Definition at line 277 of file itkNeighborhoodIterator.h. |
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Sets the pixel value located i pixels distant from the neighborhood center in the positive specified ``axis'' direction. No bounds checking is done on the size of the neighborhood. Definition at line 268 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::PixelType. |
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Set the pixel at offset o from the neighborhood center Definition at line 260 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::PixelType. |
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Set the pixel at the ith location. |
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Special SetPixel method which quietly ignores out-of-bounds attempts. Sets status TRUE if pixel has been set, FALSE otherwise. |
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Sets the pixel value located one pixel distant from the neighborhood center in the specifed negative axis direction. No bounds checking is done on the size of the neighborhood. Definition at line 293 of file itkNeighborhoodIterator.h. |
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Sets the pixel value located i pixels distant from the neighborhood center in the negative specified ``axis'' direction. No bounds checking is done on the size of the neighborhood. Definition at line 284 of file itkNeighborhoodIterator.h. References itk::NeighborhoodIterator< TImage, TBoundaryCondition >::PixelType. |
1.3.8 written by Dimitri van Heesch,
© 1997-2000