itkSigmoidImageFilter.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 itkSigmoidImageFilter_h
#define itkSigmoidImageFilter_h
 
#include "itkUnaryFunctorImageFilter.h"
#include "itkMath.h"
 
namespace itk
{
 
namespace Functor
{
template <typename TInput, typename TOutput>
class Sigmoid
{
public:
  Sigmoid()
    : m_OutputMinimum(NumericTraits<TOutput>::min())
    , m_OutputMaximum(NumericTraits<TOutput>::max())
  {}
 
  ~Sigmoid() = default;
 
 
  bool
  operator==(const Sigmoid & other) const
  {
    return Math::ExactlyEquals(m_Alpha, other.m_Alpha) && Math::ExactlyEquals(m_Beta, other.m_Beta) &&
           Math::ExactlyEquals(m_OutputMaximum, other.m_OutputMaximum) &&
           Math::ExactlyEquals(m_OutputMinimum, other.m_OutputMinimum);
  }
 
  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Sigmoid);
 
  inline TOutput
  operator()(const TInput & A) const
  {
    const double x = (static_cast<double>(A) - m_Beta) / m_Alpha;
    const double e = 1.0 / (1.0 + std::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;
  }
 
  [[nodiscard]] double
  GetAlpha() const
  {
    return m_Alpha;
  }
 
  [[nodiscard]] double
  GetBeta() const
  {
    return m_Beta;
  }
 
  void
  SetOutputMinimum(TOutput min)
  {
    m_OutputMinimum = min;
  }
 
  void
  SetOutputMaximum(TOutput max)
  {
    m_OutputMaximum = max;
  }
 
  [[nodiscard]] TOutput
  GetOutputMinimum() const
  {
    return m_OutputMinimum;
  }
 
  [[nodiscard]] TOutput
  GetOutputMaximum() const
  {
    return m_OutputMaximum;
  }
 
private:
  double  m_Alpha{ 1.0 };
  double  m_Beta{ 0.0 };
  TOutput m_OutputMinimum;
  TOutput m_OutputMaximum;
};
} // namespace Functor
 
template <typename TInputImage, typename TOutputImage>
class SigmoidImageFilter
  : public UnaryFunctorImageFilter<TInputImage,
                                   TOutputImage,
                                   Functor::Sigmoid<typename TInputImage::PixelType, typename TOutputImage::PixelType>>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SigmoidImageFilter);

  using Self = SigmoidImageFilter;
  using Superclass =
    UnaryFunctorImageFilter<TInputImage,
                            TOutputImage,
                            Functor::Sigmoid<typename TInputImage::PixelType, typename TOutputImage::PixelType>>;
 
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
 
  using OutputPixelType = typename TOutputImage::PixelType;

  itkNewMacro(Self);

  itkOverrideGetNameOfClassMacro(SigmoidImageFilter);
 
  void
  SetAlpha(double alpha)
  {
    if (Math::ExactlyEquals(alpha, this->GetFunctor().GetAlpha()))
    {
      return;
    }
    this->GetFunctor().SetAlpha(alpha);
    this->Modified();
  }
 
  [[nodiscard]] double
  GetAlpha() const
  {
    return this->GetFunctor().GetAlpha();
  }
 
  void
  SetBeta(double beta)
  {
    if (Math::ExactlyEquals(beta, this->GetFunctor().GetBeta()))
    {
      return;
    }
    this->GetFunctor().SetBeta(beta);
    this->Modified();
  }
 
  [[nodiscard]] double
  GetBeta() const
  {
    return this->GetFunctor().GetBeta();
  }
 
  void
  SetOutputMinimum(OutputPixelType min)
  {
    if (Math::ExactlyEquals(min, this->GetFunctor().GetOutputMinimum()))
    {
      return;
    }
    this->GetFunctor().SetOutputMinimum(min);
    this->Modified();
  }
 
  OutputPixelType
  GetOutputMinimum() const
  {
    return this->GetFunctor().GetOutputMinimum();
  }
 
  void
  SetOutputMaximum(OutputPixelType max)
  {
    if (Math::ExactlyEquals(max, this->GetFunctor().GetOutputMaximum()))
    {
      return;
    }
    this->GetFunctor().SetOutputMaximum(max);
    this->Modified();
  }
 
  OutputPixelType
  GetOutputMaximum() const
  {
    return this->GetFunctor().GetOutputMaximum();
  }
 
  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>));
 
protected:
  SigmoidImageFilter() = default;
  ~SigmoidImageFilter() override = default;
};
} // end namespace itk
 
#endif