itkCacheableScalarFunction.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 itkCacheableScalarFunction_h
#define itkCacheableScalarFunction_h
 
#include "itkArray.h"
#include "itkIntTypes.h"
#include "ITKBiasCorrectionExport.h"
 
namespace itk
{
class ITKBiasCorrection_EXPORT CacheableScalarFunction
{
public:
  CacheableScalarFunction();

  virtual ~CacheableScalarFunction();

  using MeasureType = double;
  using MeasureArrayType = Array<MeasureType>;

  SizeValueType
  GetNumberOfSamples() const
  {
    return m_NumberOfSamples;
  }

  bool
  IsCacheAvailable() const
  {
    return m_CacheAvailable;
  }

  double
  GetCacheUpperBound() const
  {
    return m_CacheUpperBound;
  }

  double
  GetCacheLowerBound() const
  {
    return m_CacheLowerBound;
  }

  virtual MeasureType
  Evaluate(MeasureType x);

  double
  GetInterval() const
  {
    return m_TableInc;
  }

  inline MeasureType
  GetCachedValue(MeasureType x)
  {
    if (x > m_CacheUpperBound || x < m_CacheLowerBound)
    {
      throw ExceptionObject(__FILE__, __LINE__);
    }
    // access table
    auto index = static_cast<int>((x - m_CacheLowerBound) / m_TableInc);
    return m_CacheTable[index];
  }
 
protected:
  void
  CreateCache(double lowerBound, double upperBound, SizeValueType sampleSize);
 
private:
  SizeValueType m_NumberOfSamples{ 0 };

  MeasureArrayType m_CacheTable{};

  double m_CacheUpperBound{ 0.0 };

  double m_CacheLowerBound{ 0.0 };

  double m_TableInc{ 0.0 };

  bool m_CacheAvailable{ false };
}; // end of class
} // end of namespace itk
#endif