SphinxExamples/src/Nonunit/Review/SinglephaseChanAndVeseSparseFieldLevelSetSegmentation/Code.cxx

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// The use of the ScalarChanAndVeseSparseLevelSetImageFilter is
// illustrated in the following example. The implementation of this filter in
// ITK is based on the paper by Chan And Vese.  This
// implementation extends the functionality of the
// level-set filters in ITK by using region-based variational techniques. These methods
// do not rely on the presence of edges in the images.
//
// ScalarChanAndVeseSparseLevelSetImageFilter expects two inputs.  The first is
// an initial level set in the form of an \doxygen{Image}. The second input
// is a feature image. For this algorithm, the feature image is the original
// raw or preprocessed image. Several parameters are required by the algorithm
// for regularization and weights of different energy terms. The user is encouraged to
// change different parameter settings to optimize the code example on their images.
//
// Let's start by including the headers of the main filters involved in the
// preprocessing.
//
 
 
#include "itkScalarChanAndVeseSparseLevelSetImageFilter.h"
#include "itkScalarChanAndVeseLevelSetFunctionData.h"
#include "itkConstrainedRegionBasedLevelSetFunctionSharedData.h"
#include "itkFastMarchingImageFilter.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkImage.h"
#include "itkAtanRegularizedHeavisideStepFunction.h"
 
int
main(int argc, char ** argv)
{
  if (argc < 6)
  {
    std::cerr << "Missing arguments" << std::endl;
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << " featureImage outputImage";
    std::cerr << " startx starty seedValue" << std::endl;
    return EXIT_FAILURE;
  }
 
  unsigned int nb_iteration = 500;
  double       rms = 0.;
  double       epsilon = 1.;
  double       curvature_weight = 0.;
  double       area_weight = 0.;
  double       reinitialization_weight = 0.;
  double       volume_weight = 0.;
  double       volume = 0.;
  double       l1 = 1.;
  double       l2 = 1.;
 
  //
  //  We now define the image type using a particular pixel type and
  //  dimension. In this case the \code{float} type is used for the pixels
  //  due to the requirements of the smoothing filter.
  //
  constexpr unsigned int Dimension = 2;
  using ScalarPixelType = float;
  using InternalImageType = itk::Image<ScalarPixelType, Dimension>;
 
 
  using DataHelperType = itk::ScalarChanAndVeseLevelSetFunctionData<InternalImageType, InternalImageType>;
 
  using SharedDataHelperType =
    itk::ConstrainedRegionBasedLevelSetFunctionSharedData<InternalImageType, InternalImageType, DataHelperType>;
 
  using LevelSetFunctionType =
    itk::ScalarChanAndVeseLevelSetFunction<InternalImageType, InternalImageType, SharedDataHelperType>;
 
 
  //  We declare now the type of the numerically discretized Step and Delta functions that
  //  will be used in the level-set computations for foreground and background regions
  //
  using DomainFunctionType = itk::AtanRegularizedHeavisideStepFunction<ScalarPixelType, ScalarPixelType>;
 
  auto domainFunction = DomainFunctionType::New();
  domainFunction->SetEpsilon(epsilon);
 
  InternalImageType::Pointer featureImage = itk::ReadImage<InternalImageType>(argv[1]);
 
  //  We declare now the type of the FastMarchingImageFilter that
  //  will be used to generate the initial level set in the form of a distance
  //  map.
  //
  using FastMarchingFilterType = itk::FastMarchingImageFilter<InternalImageType, InternalImageType>;
 
  auto fastMarching = FastMarchingFilterType::New();
 
  //  The FastMarchingImageFilter requires the user to provide a seed
  //  point from which the level set will be generated. The user can actually
  //  pass not only one seed point but a set of them. Note the the
  //  FastMarchingImageFilter is used here only as a helper in the
  //  determination of an initial level set. We could have used the
  //  \doxygen{DanielssonDistanceMapImageFilter} in the same way.
  //
  //  The seeds are passed stored in a container. The type of this
  //  container is defined as \code{NodeContainer} among the
  //  FastMarchingImageFilter traits.
  //
  using NodeContainer = FastMarchingFilterType::NodeContainer;
  using NodeType = FastMarchingFilterType::NodeType;
 
  auto seeds = NodeContainer::New();
 
  InternalImageType::IndexType seedPosition;
 
  seedPosition[0] = std::stoi(argv[3]);
  seedPosition[1] = std::stoi(argv[4]);
 
  const double initialDistance = std::stod(argv[5]);
 
  NodeType node;
 
  const double seedValue = -initialDistance;
 
  node.SetValue(seedValue);
  node.SetIndex(seedPosition);
 
  //  The list of nodes is initialized and then every node is inserted using
  //  the \code{InsertElement()}.
  //
  seeds->Initialize();
  seeds->InsertElement(0, node);
 
 
  //  The set of seed nodes is passed now to the
  //  FastMarchingImageFilter with the method
  //  \code{SetTrialPoints()}.
  //
  fastMarching->SetTrialPoints(seeds);
 
 
  //  Since the FastMarchingImageFilter is used here just as a
  //  Distance Map generator. It does not require a speed image as input.
  //  Instead the constant value $1.0$ is passed using the
  //  \code{SetSpeedConstant()} method.
  //
  fastMarching->SetSpeedConstant(1.0);
 
  //  The FastMarchingImageFilter requires the user to specify the
  //  size of the image to be produced as output. This is done using the
  //  \code{SetOutputSize()}. Note that the size is obtained here from the
  //  output image of the smoothing filter. The size of this image is valid
  //  only after the \code{Update()} methods of this filter has been called
  //  directly or indirectly.
  //
  fastMarching->SetOutputSize(featureImage->GetBufferedRegion().GetSize());
  fastMarching->Update();
 
  //  We declare now the type of the ScalarChanAndVeseSparseLevelSetImageFilter that
  //  will be used to generate a segmentation.
  //
 
  using MultiLevelSetType = itk::ScalarChanAndVeseSparseLevelSetImageFilter<InternalImageType,
                                                                            InternalImageType,
                                                                            InternalImageType,
                                                                            LevelSetFunctionType,
                                                                            SharedDataHelperType>;
 
  auto levelSetFilter = MultiLevelSetType::New();
 
  //  We set the function count to 1 since a single level-set is being evolved.
  //
  levelSetFilter->SetFunctionCount(1);
 
  //  Set the feature image and initial level-set image as output of the
  //  fast marching image filter.
  //
  levelSetFilter->SetFeatureImage(featureImage);
  levelSetFilter->SetLevelSet(0, fastMarching->GetOutput());
 
  //  Once activiated the level set evolution will stop if the convergence
  //  criteria or if the maximum number of iterations is reached.  The
  //  convergence criteria is defined in terms of the root mean squared (RMS)
  //  change in the level set function. The evolution is said to have
  //  converged if the RMS change is below a user specified threshold.  In a
  //  real application is desirable to couple the evolution of the zero set
  //  to a visualization module allowing the user to follow the evolution of
  //  the zero set. With this feedback, the user may decide when to stop the
  //  algorithm before the zero set leaks through the regions of low gradient
  //  in the contour of the anatomical structure to be segmented.
  //
  levelSetFilter->SetNumberOfIterations(nb_iteration);
  levelSetFilter->SetMaximumRMSError(rms);
 
  //  Often, in real applications, images have different pixel resolutions. In such
  //  cases, it is best to use the native spacings to compute derivatives etc rather
  //  than sampling the images.
  //
  levelSetFilter->SetUseImageSpacing(1);
 
  //  For large images, we may want to compute the level-set over the initial supplied
  //  level-set image. This saves a lot of memory.
  //
  levelSetFilter->SetInPlace(false);
 
  //  For the level set with phase 0, set different parameters and weights. This may
  //  to be set in a loop for the case of multiple level-sets evolving simultaneously.
  //
  levelSetFilter->GetDifferenceFunction(0)->SetDomainFunction(domainFunction);
  levelSetFilter->GetDifferenceFunction(0)->SetCurvatureWeight(curvature_weight);
  levelSetFilter->GetDifferenceFunction(0)->SetAreaWeight(area_weight);
  levelSetFilter->GetDifferenceFunction(0)->SetReinitializationSmoothingWeight(reinitialization_weight);
  levelSetFilter->GetDifferenceFunction(0)->SetVolumeMatchingWeight(volume_weight);
  levelSetFilter->GetDifferenceFunction(0)->SetVolume(volume);
  levelSetFilter->GetDifferenceFunction(0)->SetLambda1(l1);
  levelSetFilter->GetDifferenceFunction(0)->SetLambda2(l2);
 
  levelSetFilter->Update();
 
  try
  {
    itk::WriteImage(levelSetFilter->GetOutput(), argv[2]);
  }
  catch (const itk::ExceptionObject & excep)
  {
    std::cerr << "Exception caught !" << std::endl;
    std::cerr << excep << std::endl;
    return -1;
  }
 
  return EXIT_SUCCESS;
}