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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkSigmoidImageFilter.h,v $
Language: C++
Date: $Date: 2007-09-16 14:41:02 $
Version: $Revision: 1.14 $
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 __itkSigmoidImageFilter_h
#define __itkSigmoidImageFilter_h
#include "itkUnaryFunctorImageFilter.h"
namespace itk
{
/** \class SigmoidImageFilter
* \brief Computes the sigmoid function pixel-wise
*
* A linear transformation is applied first on the argument of
* the sigmoid fuction. The resulting total transfrom is given by
*
* \f[
* f(x) = (Max-Min) \cdot \frac{1}{\left(1+e^{-(\frac{ x - \beta }{\alpha}\right)}} + Min
* \f]
*
* Every output pixel is equal to f(x). Where x is the intensity of the
* homologous input pixel, and alpha and beta are user-provided constants.
*
* \ingroup IntensityImageFilters Multithreaded
*
*/
namespace Function {
template< class TInput, class TOutput>
class Sigmoid
{
public:
Sigmoid() {
m_Alpha = 1.0;
m_Beta = 0.0;
m_OutputMinimum = NumericTraits< TOutput >::min();
m_OutputMaximum = NumericTraits< TOutput >::max();
}
~Sigmoid() {};
bool operator!=( const Sigmoid & other ) const
{
if( m_Alpha != other.m_Alpha ||
m_Beta != other.m_Beta ||
m_OutputMaximum != other.m_OutputMaximum ||
m_OutputMinimum != other.m_OutputMinimum )
{
return true;
}
return false;
}
bool operator==( const Sigmoid & other ) const
{
return !(*this != other);
}
inline TOutput operator()( const TInput & A )
{
const double x = ( static_cast<double>(A) - m_Beta ) / m_Alpha;
const double e = 1.0 / ( 1.0 + vcl_exp(- x ) );
const double v =
(m_OutputMaximum - m_OutputMinimum ) * e + m_OutputMinimum;
return static_cast<TOutput>( v );
}
void SetAlpha( double alpha ) {
m_Alpha = alpha;
}
void SetBeta( double beta ) {
m_Beta = beta;
}
double GetAlpha() const {
return m_Alpha;
}
double GetBeta() const {
return m_Beta;
}
void SetOutputMinimum( TOutput min ) {
m_OutputMinimum = min;
}
void SetOutputMaximum( TOutput max ) {
m_OutputMaximum = max;
}
TOutput GetOutputMinimum() const {
return m_OutputMinimum;
}
TOutput GetOutputMaximum() const {
return m_OutputMaximum;
}
private:
double m_Alpha;
double m_Beta;
TOutput m_OutputMinimum;
TOutput m_OutputMaximum;
};
}
template <class TInputImage, class TOutputImage>
class ITK_EXPORT SigmoidImageFilter :
public
UnaryFunctorImageFilter<TInputImage,TOutputImage,
Function::Sigmoid<
typename TInputImage::PixelType,
typename TOutputImage::PixelType> >
{
public:
/** Standard class typedefs. */
typedef SigmoidImageFilter Self;
typedef UnaryFunctorImageFilter<TInputImage,TOutputImage,
Function::Sigmoid< typename TInputImage::PixelType,
typename TOutputImage::PixelType> > Superclass;
typedef SmartPointer<Self> Pointer;
typedef SmartPointer<const Self> ConstPointer;
typedef typename TOutputImage::PixelType OutputPixelType;
/** Method for creation through the object factory. */
itkNewMacro(Self);
/** Macro that provides the GetNameOfClass() method */
itkTypeMacro( SigmoidImageFilter, UnaryFunctorImageFilter );
void SetAlpha( double alpha )
{
if( alpha == this->GetFunctor().GetAlpha() )
{
return;
}
this->GetFunctor().SetAlpha( alpha );
this->Modified();
}
void SetBeta( double beta )
{
if( beta == this->GetFunctor().GetBeta() )
{
return;
}
this->GetFunctor().SetBeta( beta );
this->Modified();
}
void SetOutputMinimum( OutputPixelType min )
{
if( min == this->GetFunctor().GetOutputMinimum() )
{
return;
}
this->GetFunctor().SetOutputMinimum( min );
this->Modified();
}
void SetOutputMaximum( OutputPixelType max )
{
if( max == this->GetFunctor().GetOutputMaximum() )
{
return;
}
this->GetFunctor().SetOutputMaximum( max );
this->Modified();
}
#ifdef ITK_USE_CONCEPT_CHECKING
/** Begin concept checking */
itkConceptMacro(InputConvertibleToDoubleCheck,
(Concept::Convertible<typename TInputImage::PixelType, double>));
itkConceptMacro(OutputAdditiveOperatorsCheck,
(Concept::AdditiveOperators<OutputPixelType>));
itkConceptMacro(DoubleConvertibleToOutputCheck,
(Concept::Convertible<double, OutputPixelType>));
itkConceptMacro(OutputTimesDoubleCheck,
(Concept::MultiplyOperator<OutputPixelType, double>));
itkConceptMacro(OutputDoubleAdditiveOperatorsCheck,
(Concept::AdditiveOperators<OutputPixelType, OutputPixelType, double>));
/** End concept checking */
#endif
protected:
SigmoidImageFilter() {}
virtual ~SigmoidImageFilter() {}
private:
SigmoidImageFilter(const Self&); //purposely not implemented
void operator=(const Self&); //purposely not implemented
};
} // end namespace itk
#endif
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