itkMahalanobisDistanceMembershipFunction.h

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 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
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 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
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#ifndef itkMahalanobisDistanceMembershipFunction_h
#define itkMahalanobisDistanceMembershipFunction_h
 
#include "itkNumericTraitsVectorPixel.h"
#include "itkVariableSizeMatrix.h"
 
#include "itkMembershipFunctionBase.h"
 
namespace itk::Statistics
{
 
template <typename TVector>
class ITK_TEMPLATE_EXPORT MahalanobisDistanceMembershipFunction : public MembershipFunctionBase<TVector>
{
public:
  using Self = MahalanobisDistanceMembershipFunction;
  using Superclass = MembershipFunctionBase<TVector>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkOverrideGetNameOfClassMacro(MahalanobisDistanceMembershipFunction);
  itkNewMacro(Self);
  using MembershipFunctionPointer = typename Superclass::Pointer;

  using MeasurementVectorType = TVector;

  using typename Superclass::MeasurementVectorSizeType;

  using MeasurementVectorRealType = typename itk::NumericTraits<MeasurementVectorType>::RealType;
  using MeanVectorType = MeasurementVectorRealType;

  using CovarianceMatrixType = VariableSizeMatrix<double>;

  void
  SetMean(const MeanVectorType & mean);

  itkGetConstReferenceMacro(Mean, MeanVectorType);

  void
  SetCovariance(const CovarianceMatrixType & cov);

  itkGetConstReferenceMacro(Covariance, CovarianceMatrixType);

  double
  Evaluate(const MeasurementVectorType & measurement) const override;

  [[nodiscard]] LightObject::Pointer
  InternalClone() const override;
 
protected:
  MahalanobisDistanceMembershipFunction();
  ~MahalanobisDistanceMembershipFunction() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;
 
private:
  MeanVectorType       m_Mean{};       // mean
  CovarianceMatrixType m_Covariance{}; // covariance matrix
 
  // inverse covariance matrix. automatically calculated
  // when covariance matrix is set.
  CovarianceMatrixType m_InverseCovariance{};

  bool m_CovarianceNonsingular{};
};
} // namespace itk::Statistics
 
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkMahalanobisDistanceMembershipFunction.hxx"
#endif
 
#endif