itkCompositeValleyFunction.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 itkCompositeValleyFunction_h
#define itkCompositeValleyFunction_h
 
#include "itkCacheableScalarFunction.h"
#include "ITKBiasCorrectionExport.h"
#include <vector>
 
namespace itk
{
class TargetClass
{
public:
  TargetClass(double mean, double sigma)
    : m_Mean(mean)
    , m_Sigma(sigma)
  {}

  void
  SetMean(double mean)
  {
    m_Mean = mean;
  }
  [[nodiscard]] double
  GetMean() const
  {
    return m_Mean;
  }

  void
  SetSigma(double sigma)
  {
    m_Sigma = sigma;
  }
  [[nodiscard]] double
  GetSigma() const
  {
    return m_Sigma;
  }

private:
  double m_Mean;
  double m_Sigma;
}; // end of class
 
class ITKBiasCorrection_EXPORT CompositeValleyFunction : public CacheableScalarFunction
{
public:
  using Superclass = CacheableScalarFunction;

  using MeasureType = Superclass::MeasureType;
  using MeasureArrayType = Superclass::MeasureArrayType;

  CompositeValleyFunction(const MeasureArrayType & classMeans, const MeasureArrayType & classSigmas);

  ~CompositeValleyFunction() override;

  [[nodiscard]] double
  GetUpperBound() const
  {
    return m_UpperBound;
  }

  [[nodiscard]] double
  GetLowerBound() const
  {
    return m_LowerBound;
  }

  MeasureType
  operator()(MeasureType x)
  {
    if (x > m_UpperBound || x < m_LowerBound)
    {
      return 1;
    }
 
    if (!this->IsCacheAvailable())
    {
      return this->Evaluate(x);
    }
 
    return GetCachedValue(x);
  }

  MeasureType
  Evaluate(MeasureType x) override;

  inline MeasureType
  valley(MeasureType d)
  {
    return 1 - 1 / (1 + d * d / 3);
  }
 
protected:
  void
  AddNewClass(double mean, double sigma)
  {
    const TargetClass aClass(mean, sigma);
 
    m_Targets.push_back(aClass);
  }

  void
  Initialize();
 
private:
  std::vector<TargetClass> m_Targets{};

  double m_UpperBound{};

  double m_LowerBound{};
}; // end of class
} // end of namespace itk
#endif