itkNormalVectorDiffusionFunction.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
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  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.
 *
 *=========================================================================*/
#ifndef itkNormalVectorDiffusionFunction_h
#define itkNormalVectorDiffusionFunction_h
 
#include "itkNormalVectorFunctionBase.h"
#include "itkNumericTraits.h"
#include <cmath>
 
namespace itk
{
template <typename TSparseImageType>
class ITK_TEMPLATE_EXPORT NormalVectorDiffusionFunction : public NormalVectorFunctionBase<TSparseImageType>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(NormalVectorDiffusionFunction);

  using Self = NormalVectorDiffusionFunction;
  using Superclass = NormalVectorFunctionBase<TSparseImageType>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkOverrideGetNameOfClassMacro(NormalVectorDiffusionFunction);

  static constexpr unsigned int ImageDimension = Superclass::ImageDimension;

  itkNewMacro(Self);

  using typename Superclass::TimeStepType;
  using typename Superclass::RadiusType;
  using typename Superclass::NeighborhoodType;
  using typename Superclass::NeighborhoodScalesType;
  using typename Superclass::FloatOffsetType;
  using typename Superclass::IndexType;
  using typename Superclass::SparseImageType;
  using typename Superclass::NodeType;
  using typename Superclass::NodeValueType;
  using typename Superclass::NormalVectorType;

  void
  SetNormalProcessType(int npt)
  {
    m_NormalProcessType = npt;
  }

  int
  GetNormalProcessType() const
  {
    return m_NormalProcessType;
  }

  void
  SetConductanceParameter(NodeValueType cp)
  {
    m_ConductanceParameter = cp + static_cast<NodeValueType>(0.001);
    // we add a minimum conductance to avoid divide by zero
    // can make this a parameter.
    m_FluxStopConstant = static_cast<NodeValueType>(-1.0 / (m_ConductanceParameter * m_ConductanceParameter));
  }


  NodeValueType
  GetConductanceParameter() const
  {
    return m_ConductanceParameter;
  }

  NodeValueType
  GetFluxStopConstant() const
  {
    return m_FluxStopConstant;
  }

  void
  PrecomputeSparseUpdate(NeighborhoodType & it) const override;

  NormalVectorType
  ComputeSparseUpdate(NeighborhoodType & it, void * globalData, const FloatOffsetType & offset) const override;
 
protected:
  NormalVectorDiffusionFunction();
  ~NormalVectorDiffusionFunction() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  NodeValueType
  FluxStopFunction(const NodeValueType v) const
  {
    // the slow exp function could be replaced with a lookup table
    if (v <= 0.0)
    {
      return NumericTraits<NodeValueType>::OneValue();
    }
 
    return static_cast<NodeValueType>(std::exp(m_FluxStopConstant * v));
  }
 
private:
  NodeValueType m_ConductanceParameter{};

  NodeValueType m_FluxStopConstant{};

  int m_NormalProcessType{};
};
} // end namespace itk
 
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkNormalVectorDiffusionFunction.hxx"
#endif
 
#endif