text: /*=========================================================================
   *
   *  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
   *
   *         http://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 itkMeanProjectionImageFilter_h
  #define itkMeanProjectionImageFilter_h
  
  #include "itkProjectionImageFilter.h"
  #include "itkConceptChecking.h"
  
  namespace itk
  {
  /** \class MeanProjectionImageFilter
   * \brief Mean projection
   *
   * This class was contributed to the Insight Journal by Gaetan Lehmann.
   * The original paper can be found at
   * https://www.insight-journal.org/browse/publication/71
   *
   * \author Gaetan Lehmann. Biologie du Developpement et de la Reproduction,
   * INRA de Jouy-en-Josas, France.
   *
   * \sa ProjectionImageFilter
   * \sa MedianProjectionImageFilter
   * \sa MinimumProjectionImageFilter
   * \sa StandardDeviationProjectionImageFilter
   * \sa SumProjectionImageFilter
   * \sa BinaryProjectionImageFilter
   * \sa MaximumProjectionImageFilter
   * \ingroup ITKImageStatistics
   */
  
  namespace Functor
  {
  template <typename TInputPixel, typename TAccumulate>
  class MeanAccumulator
  {
  public:
    using RealType = typename NumericTraits<TInputPixel>::RealType;
  
    MeanAccumulator(SizeValueType size) { m_Size = size; }
  
    ~MeanAccumulator() { m_Size = NumericTraits<SizeValueType>::ZeroValue(); }
  
    inline void
    Initialize()
    {
      m_Sum = NumericTraits<TAccumulate>::ZeroValue();
    }
  
    inline void
    operator()(const TInputPixel & input)
    {
      m_Sum = m_Sum + input;
    }
  
    inline RealType
    GetValue()
    {
      return ((RealType)m_Sum) / m_Size;
    }
  
    TAccumulate   m_Sum;
    SizeValueType m_Size;
  };
  } // namespace Functor
  
  template <typename TInputImage,
            typename TOutputImage,
            typename TAccumulate = typename NumericTraits<typename TOutputImage::PixelType>::AccumulateType>
  class MeanProjectionImageFilter
    : public ProjectionImageFilter<TInputImage,
                                   TOutputImage,
                                   Functor::MeanAccumulator<typename TInputImage::PixelType, TAccumulate>>
  {
  public:
    ITK_DISALLOW_COPY_AND_MOVE(MeanProjectionImageFilter);
  
    using Self = MeanProjectionImageFilter;
    using Superclass = ProjectionImageFilter<TInputImage,
                                             TOutputImage,
                                             Functor::MeanAccumulator<typename TInputImage::PixelType, TAccumulate>>;
  
    using Pointer = SmartPointer<Self>;
    using ConstPointer = SmartPointer<const Self>;
  
    using InputImageType = TInputImage;
    using InputPixelType = typename InputImageType::PixelType;
  
    using OutputImageType = TOutputImage;
    using OutputPixelType = typename OutputImageType::PixelType;
  
    /** Runtime information support. */
    itkTypeMacro(MeanProjectionImageFilter, ProjectionImageFilter);
  
    /** Method for creation through the object factory. */
    itkNewMacro(Self);
  
  #ifdef ITK_USE_CONCEPT_CHECKING
    // Begin concept checking
    itkConceptMacro(InputPixelToOutputPixelTypeGreaterAdditiveOperatorCheck,
                    (Concept::AdditiveOperators<OutputPixelType, InputPixelType, OutputPixelType>));
  
    itkConceptMacro(InputHasNumericTraitsCheck, (Concept::HasNumericTraits<InputPixelType>));
    // End concept checking
  #endif
  
  protected:
    MeanProjectionImageFilter() = default;
    ~MeanProjectionImageFilter() override = default;
  }; // end MeanProjectionImageFilter
  } // end namespace itk
  
  #endif
  