itkGradientDifferenceImageToImageMetric.h

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 *  Copyright Insight Software Consortium
 *
 *  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
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 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
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 *  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 itkGradientDifferenceImageToImageMetric_h
#define itkGradientDifferenceImageToImageMetric_h

#include "itkImageToImageMetric.h"

#include "itkSobelOperator.h"
#include "itkNeighborhoodOperatorImageFilter.h"
#include "itkPoint.h"
#include "itkCastImageFilter.h"
#include "itkResampleImageFilter.h"

namespace itk
{
template< typename TFixedImage, typename TMovingImage >
class ITK_TEMPLATE_EXPORT GradientDifferenceImageToImageMetric:
  public ImageToImageMetric< TFixedImage, TMovingImage >
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(GradientDifferenceImageToImageMetric);

  using Self = GradientDifferenceImageToImageMetric;
  using Superclass = ImageToImageMetric< TFixedImage, TMovingImage >;

  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

  itkNewMacro(Self);

  itkTypeMacro(GradientDifferenceImageToImageMetric, ImageToImageMetric);

  using RealType = typename Superclass::RealType;
  using TransformType = typename Superclass::TransformType;
  using TransformPointer = typename Superclass::TransformPointer;
  using TransformParametersType = typename Superclass::TransformParametersType;
  using TransformJacobianType = typename Superclass::TransformJacobianType;

  using MeasureType = typename Superclass::MeasureType;
  using DerivativeType = typename Superclass::DerivativeType;
  using FixedImageType = typename Superclass::FixedImageType;
  using MovingImageType = typename Superclass::MovingImageType;
  using FixedImageConstPointer = typename Superclass::FixedImageConstPointer;
  using MovingImageConstPointer = typename Superclass::MovingImageConstPointer;

  using FixedImagePixelType = typename TFixedImage::PixelType;
  using MovedImagePixelType = typename TMovingImage::PixelType;

  static constexpr unsigned int FixedImageDimension = TFixedImage::ImageDimension;
  using TransformedMovingImageType = itk::Image< FixedImagePixelType,
                      Self::FixedImageDimension >;

  using TransformMovingImageFilterType =
      itk::ResampleImageFilter< MovingImageType, TransformedMovingImageType >;

  using FixedGradientImageType = itk::Image< RealType, Self::FixedImageDimension >;

  using CastFixedImageFilterType = itk::CastImageFilter< FixedImageType, FixedGradientImageType >;
  using CastFixedImageFilterPointer = typename CastFixedImageFilterType::Pointer;

  using FixedGradientPixelType = typename FixedGradientImageType::PixelType;

  static constexpr unsigned int MovedImageDimension = MovingImageType::ImageDimension;

  using MovedGradientImageType = itk::Image< RealType, Self::MovedImageDimension >;

  using CastMovedImageFilterType = itk::CastImageFilter< TransformedMovingImageType, MovedGradientImageType >;
  using CastMovedImageFilterPointer = typename CastMovedImageFilterType::Pointer;

  using MovedGradientPixelType = typename MovedGradientImageType::PixelType;

  void GetDerivative(const TransformParametersType & parameters,
                     DerivativeType  & derivative) const override;

  MeasureType GetValue(const TransformParametersType & parameters) const override;

  void GetValueAndDerivative(const TransformParametersType & parameters,
                             MeasureType & Value, DerivativeType & derivative) const override;

  void Initialize() override;

  void WriteGradientImagesToFiles() const;

  itkSetMacro(DerivativeDelta, double);
  itkGetConstReferenceMacro(DerivativeDelta, double);

protected:
  GradientDifferenceImageToImageMetric();
  ~GradientDifferenceImageToImageMetric() override = default;
  void PrintSelf(std::ostream & os, Indent indent) const override;

  void ComputeMovedGradientRange() const;

  void ComputeVariance() const;

  MeasureType ComputeMeasure(const TransformParametersType & parameters,
                             const double *subtractionFactor) const;

  using FixedSobelFilter = NeighborhoodOperatorImageFilter<
    FixedGradientImageType, FixedGradientImageType >;

  using MovedSobelFilter = NeighborhoodOperatorImageFilter<
    MovedGradientImageType, MovedGradientImageType >;

private:
  mutable MovedGradientPixelType m_Variance[FixedImageDimension];

  mutable MovedGradientPixelType m_MinMovedGradient[MovedImageDimension];
  mutable MovedGradientPixelType m_MaxMovedGradient[MovedImageDimension];

  mutable FixedGradientPixelType m_MinFixedGradient[FixedImageDimension];
  mutable FixedGradientPixelType m_MaxFixedGradient[FixedImageDimension];

  typename TransformMovingImageFilterType::Pointer m_TransformMovingImageFilter;

  CastFixedImageFilterPointer m_CastFixedImageFilter;

  SobelOperator< FixedGradientPixelType,
                 Self::FixedImageDimension >
  m_FixedSobelOperators[FixedImageDimension];

  typename FixedSobelFilter::Pointer m_FixedSobelFilters[Self::FixedImageDimension];

  ZeroFluxNeumannBoundaryCondition< MovedGradientImageType > m_MovedBoundCond;
  ZeroFluxNeumannBoundaryCondition< FixedGradientImageType > m_FixedBoundCond;

  CastMovedImageFilterPointer m_CastMovedImageFilter;

  SobelOperator< MovedGradientPixelType,
                 Self::MovedImageDimension >
  m_MovedSobelOperators[MovedImageDimension];

  typename MovedSobelFilter::Pointer m_MovedSobelFilters[Self::MovedImageDimension];

  double m_DerivativeDelta;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkGradientDifferenceImageToImageMetric.hxx"
#endif

#endif