/*
 * Copyright (C) 2005-2020 Centre National d'Etudes Spatiales (CNES)
 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * 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
 *
 * 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 otbVarianceImageFilter_h
#define otbVarianceImageFilter_h

#include "itkImageToImageFilter.h"
#include "itkImage.h"
#include "itkNumericTraits.h"

namespace otb
{
/** \class VarianceImageFilter
 * \brief Applies an averaging filter to an image
 *
 * Computes an image where a given pixel is the value over the standard 8, 26, etc. connected
 * neighborhood. This calculation uses a ZeroFluxNeumannBoundaryCondition.
 *
 *
 * \sa Image
 * \sa Neighborhood
 * \sa NeighborhoodOperator
 * \sa NeighborhoodIterator
 *
 * \ingroup IntensityImageFilters
 *
 * \ingroup OTBStatistics
 */
template <class TInputImage, class TOutputImage>
class ITK_EXPORT VarianceImageFilter : public itk::ImageToImageFilter<TInputImage, TOutputImage>
{
public:
  /** Extract dimension from input and output image. */
  itkStaticConstMacro(InputImageDimension, unsigned int, TInputImage::ImageDimension);
  itkStaticConstMacro(OutputImageDimension, unsigned int, TOutputImage::ImageDimension);

  /** Convenient typedefs for simplifying declarations. */
  typedef TInputImage  InputImageType;
  typedef TOutputImage OutputImageType;

  /** Standard class typedefs. */
  typedef VarianceImageFilter Self;
  typedef itk::ImageToImageFilter<InputImageType, OutputImageType> Superclass;
  typedef itk::SmartPointer<Self>       Pointer;
  typedef itk::SmartPointer<const Self> ConstPointer;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Run-time type information (and related methods). */
  itkTypeMacro(VarianceImageFilter, ImageToImageFilter);

  /** Image typedef support. */
  typedef typename InputImageType::PixelType                    InputPixelType;
  typedef typename OutputImageType::PixelType                   OutputPixelType;
  typedef typename itk::NumericTraits<InputPixelType>::RealType InputRealType;

  typedef typename InputImageType::RegionType  InputImageRegionType;
  typedef typename OutputImageType::RegionType OutputImageRegionType;

  typedef typename InputImageType::SizeType InputSizeType;

  /** Set the radius of the neighborhood used to compute the mean. */
  itkSetMacro(Radius, InputSizeType);

  /** Get the radius of the neighborhood used to compute the mean */
  itkGetConstReferenceMacro(Radius, InputSizeType);

  /** VarianceImageFilter needs a larger input requested region than
   * the output requested region.  As such, VarianceImageFilter needs
   * to provide an implementation for GenerateInputRequestedRegion()
   * in order to inform the pipeline execution model.
   *
   * \sa ImageToImageFilter::GenerateInputRequestedRegion() */
  void GenerateInputRequestedRegion() override;

#ifdef ITK_USE_CONCEPT_CHECKING
  /** Begin concept checking */
  itkConceptMacro(InputHasNumericTraitsCheck, (itk::Concept::HasNumericTraits<InputPixelType>));
/** End concept checking */
#endif

protected:
  VarianceImageFilter();
  ~VarianceImageFilter() override
  {
  }
  void PrintSelf(std::ostream& os, itk::Indent indent) const override;

  /** VarianceImageFilter can be implemented as a multithreaded filter.
   * Therefore, this implementation provides a ThreadedGenerateData()
   * routine which is called for each processing thread. The output
   * image data is allocated automatically by the superclass prior to
   * calling ThreadedGenerateData().  ThreadedGenerateData can only
   * write to the portion of the output image specified by the
   * parameter "outputRegionForThread"
   *
   * \sa ImageToImageFilter::ThreadedGenerateData(),
   *     ImageToImageFilter::GenerateData() */
  void ThreadedGenerateData(const OutputImageRegionType& outputRegionForThread, itk::ThreadIdType threadId) override;

private:
  VarianceImageFilter(const Self&) = delete;
  void operator=(const Self&) = delete;

  InputSizeType m_Radius;
};

} // end namespace otb

#ifndef OTB_MANUAL_INSTANTIATION
#include "otbVarianceImageFilter.hxx"
#endif

#endif
