itkNormalVectorDiffusionFunction.h

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/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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_ASSIGN(NormalVectorDiffusionFunction);

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

  itkTypeMacro(NormalVectorDiffusionFunction, NormalVectorFunctionBase);

  static constexpr unsigned int ImageDimension = Superclass::ImageDimension;

  itkNewMacro(Self);

  using TimeStepType = typename Superclass::TimeStepType;
  using RadiusType = typename Superclass::RadiusType;
  using NeighborhoodType = typename Superclass::NeighborhoodType;
  using NeighborhoodScalesType = typename Superclass::NeighborhoodScalesType;
  using FloatOffsetType = typename Superclass::FloatOffsetType;
  using IndexType = typename Superclass::IndexType;
  using SparseImageType = typename Superclass::SparseImageType;
  using NodeType = typename Superclass::NodeType;
  using NodeValueType = typename Superclass::NodeValueType;
  using NormalVectorType = 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 & neighborhood,
                                               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(); }
    else { 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