Iterate Over Image While Skipping Specific Region#

Synopsis#

Iterator over an image skipping a specified region.

Results#

Output:

0
0
0
0
0
0
Visited 6

Code#

C++#

#include "itkImage.h"
#include "itkImageRegionExclusionConstIteratorWithIndex.h"

namespace
{
using ImageType = itk::Image<int, 2>;
}

static void CreateImage(ImageType::Pointer);

int
main()
{

  auto exclusionRegionSize = ImageType::SizeType::Filled(2);

  ImageType::IndexType exclusionRegionIndex{};

  ImageType::RegionType exclusionRegion(exclusionRegionIndex, exclusionRegionSize);

  auto image = ImageType::New();
  CreateImage(image);

  itk::ImageRegionExclusionConstIteratorWithIndex<ImageType> imageIterator(image, image->GetLargestPossibleRegion());
  imageIterator.SetExclusionRegion(exclusionRegion);

  unsigned int numberVisited = 0;
  while (!imageIterator.IsAtEnd())
  {
    std::cout << imageIterator.Get() << std::endl;
    ++imageIterator;
    ++numberVisited;
  }

  std::cout << "Visited " << numberVisited << std::endl;

  return EXIT_SUCCESS;
}

void
CreateImage(ImageType::Pointer image)
{
  auto regionSize = ImageType::SizeType::Filled(3);

  ImageType::IndexType regionIndex{};

  ImageType::RegionType region(regionIndex, regionSize);

  image->SetRegions(region);
  image->Allocate();
  image->FillBuffer(0);
}

Classes demonstrated#

template<typename TImage> class ImageRegionExclusionConstIteratorWithIndex : public itk::ImageRegionConstIteratorWithIndex<TImage>

A multi-dimensional image iterator that walks an image region, excluding a second region that may partially or completely overlap the first, with read-only access to pixels.

ImageRegionExclusionConstIteratorWithIndex is a class templated over the image type that represents a multi-dimensional iterator. The exclusion region is set after construction. By default the exclusion region is empty and the iterator will behave as the itk::ImageRegionConstIteratorWithIndex with a penalty in performance due to internal bounds checking. There are no restrictions on valid exclusion regions.

As with other ITK image iterators, ImageRegionExclusionConstIteratorWithIndex requires that more information be specified before the iterator can be used than conventional iterators. Whereas the std::vector::iterator from the STL only needs to be passed a pointer to establish the iterator, the multi-dimensional image iterator needs a pointer, the size of the buffer, the size of the region, the start index of the buffer, and the start index of the region. To gain access to this information, ImageRegionExclusionConstIteratorWithIndex holds a reference to the image over which it is traversing.

ImageRegionExclusionConstIteratorWithIndex assumes a particular layout of the image data. The is arranged in a 1D array as if it were [][][][slice][row][col] with Index[0] = col, Index[1] = row, Index[2] = slice, etc.

The operator++ method provides a simple syntax for walking around a region of a multidimensional image. operator++ iterates across a row, constraining the movement to within a region of image. When the iterator reaches the boundary of the region along a row, the iterator automatically wraps to the next row, starting at the first pixel in the row that is part of the region. This allows for simple processing loops of the form:

IteratorType it( image, image->GetRequestedRegion() );

it.SetExclusionRegion( exclusionRegion );
it.GoToBegin();

while( ! it.IsAtEnd() )
{
  it.Set( 100.0 + it.Get() );
  ++it;
}

It also can be used for walking in the reverse direction like

IteratorType it( image, image->GetRequestedRegion() );

it.SetExclusionRegion( exclusionRegion );
it.GoToEnd();

while( !it.IsAtBegin() )
{
  it.Set( 100.0 );
  --it;
}

See also

ImageConstIterator

See also

ConditionalConstIterator

See also

ConstNeighborhoodIterator

See also

ConstShapedNeighborhoodIterator

See also

ConstSliceIterator

See also

CorrespondenceDataStructureIterator

See also

FloodFilledFunctionConditionalConstIterator

See also

FloodFilledImageFunctionConditionalConstIterator

See also

FloodFilledImageFunctionConditionalIterator

See also

FloodFilledSpatialFunctionConditionalConstIterator

See also

FloodFilledSpatialFunctionConditionalIterator

See also

ImageConstIterator

See also

ImageConstIteratorWithIndex

See also

ImageIterator

See also

ImageIteratorWithIndex

See also

ImageLinearConstIteratorWithIndex

See also

ImageLinearIteratorWithIndex

See also

ImageRandomConstIteratorWithIndex

See also

ImageRandomIteratorWithIndex

See also

ImageRegionConstIterator

See also

ImageRegionConstIteratorWithIndex

See also

ImageRegionExclusionConstIteratorWithIndex

See also

ImageRegionExclusionIteratorWithIndex

See also

ImageRegionIterator

See also

ImageRegionIteratorWithIndex

See also

ImageRegionReverseConstIterator

See also

ImageRegionReverseIterator

See also

ImageReverseConstIterator

See also

ImageReverseIterator

See also

ImageSliceConstIteratorWithIndex

See also

ImageSliceIteratorWithIndex

See also

NeighborhoodIterator

See also

PathConstIterator

See also

PathIterator

See also

ShapedNeighborhoodIterator

See also

SliceIterator

See also

ImageConstIteratorWithIndex

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.

ITK Sphinx Examples:

All ITK Sphinx Examples

Iterate Over Image While Skipping Specific Region

Subclassed by itk::ImageRegionExclusionIteratorWithIndex< TImage >

See itk::ImageRegionExclusionConstIteratorWithIndex for additional documentation.