itkNormalVectorDiffusionFunction.h

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/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkNormalVectorDiffusionFunction.h,v $
  Language:  C++
  Date:      $Date: 2008-03-03 13:58:44 $
  Version:   $Revision: 1.6 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

     =========================================================================*/
#ifndef __itkNormalVectorDiffusionFunction_h_
#define __itkNormalVectorDiffusionFunction_h_

#include "itkNormalVectorFunctionBase.h"
#include "itkNumericTraits.h"
#include <math.h>

namespace itk {

template <class TSparseImageType>
class ITK_EXPORT NormalVectorDiffusionFunction 
  :public NormalVectorFunctionBase <TSparseImageType>
{
public:
  typedef NormalVectorDiffusionFunction Self;
  typedef NormalVectorFunctionBase <TSparseImageType> Superclass;
  typedef SmartPointer<Self> Pointer;
  typedef SmartPointer<const Self> ConstPointer;

  itkTypeMacro( NormalVectorDiffusionFunction, NormalVectorFunctionBase);

  itkStaticConstMacro(ImageDimension, unsigned int, Superclass::ImageDimension);

  itkNewMacro(Self);

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

  virtual void PrecomputeSparseUpdate( NeighborhoodType &it ) const;

  virtual NormalVectorType ComputeSparseUpdate (NeighborhoodType &neighborhood,
                                                void *globalData,
                                                const FloatOffsetType &offset) const;

private:
  NodeValueType m_ConductanceParameter;

  NodeValueType m_FluxStopConstant;

protected:
  NormalVectorDiffusionFunction();
  ~NormalVectorDiffusionFunction() {}
  void PrintSelf(std::ostream& os, Indent indent) const;

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

private:
  int m_NormalProcessType; 

  NormalVectorDiffusionFunction(const Self&); //purposely not implemented
  void operator=(const Self&);                //purposely not implemented
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkNormalVectorDiffusionFunction.txx"
#endif

#endif

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