itkRegularizedHeavisideStepFunction.h

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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkRegularizedHeavisideStepFunction.h,v $
  Language:  C++
  Date:      $Date: 2009-05-09 21:06:28 $
  Version:   $Revision: 1.1 $

  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 __itkRegularizedHeavisideStepFunction_h
#define __itkRegularizedHeavisideStepFunction_h

#include "itkHeavisideStepFunctionBase.h"
#include "itkNumericTraits.h"
#include "vnl/vnl_math.h"

namespace itk
{

template< class TInput = float, class TOutput = double >
class RegularizedHeavisideStepFunction : public HeavisideStepFunctionBase< TInput, TOutput >
{
public:
  typedef RegularizedHeavisideStepFunction                Self;
  typedef HeavisideStepFunctionBase< TInput, TOutput >    Superclass;
  typedef SmartPointer<Self>                              Pointer;
  typedef SmartPointer<const Self>                        ConstPointer;

  typedef typename Superclass::InputType                  InputType;
  typedef typename Superclass::OutputType                 OutputType;

  typedef typename NumericTraits< InputType >::RealType            RealType;

  virtual OutputType Evaluate( const InputType& input ) const = 0;

  virtual OutputType EvaluateDerivative( const InputType& input ) const = 0;

  void SetEpsilon( const RealType & ieps )
    {
    this->m_Epsilon = ieps;

    if ( ieps > vnl_math::eps )
      {
      m_OneOverEpsilon = 1.0 / ieps;
      }
    else
      {
      itkGenericExceptionMacro("ERROR: Epsilon needs to be greater than " << vnl_math::eps );
      }
    }

  RealType GetEpsilon() const
    {
    return this->m_Epsilon;
    }

  RealType GetOneOverEpsilon() const
    {
    return this->m_OneOverEpsilon;
    }

protected:
  RegularizedHeavisideStepFunction()
    {
    this->m_Epsilon = 1.0;
    this->m_OneOverEpsilon = 1.0;
    }

  virtual ~RegularizedHeavisideStepFunction() {}

private:
  RegularizedHeavisideStepFunction(const Self& ); //purposely not implemented
  void operator=(const Self& ); //purposely not implemented

  RealType      m_Epsilon;
  RealType      m_OneOverEpsilon;
};

}

#endif