itkMutualInformationImageToImageMetric.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 itkMutualInformationImageToImageMetric_h
#define itkMutualInformationImageToImageMetric_h
 
#include "itkImageToImageMetric.h"
#include "itkPoint.h"
 
#include "itkIndex.h"
#include "itkKernelFunctionBase.h"
 
namespace itk
{
template <typename TFixedImage, typename TMovingImage>
class ITK_TEMPLATE_EXPORT MutualInformationImageToImageMetric : public ImageToImageMetric<TFixedImage, TMovingImage>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(MutualInformationImageToImageMetric);

  using Self = MutualInformationImageToImageMetric;
  using Superclass = ImageToImageMetric<TFixedImage, TMovingImage>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkNewMacro(Self);

  itkOverrideGetNameOfClassMacro(MutualInformationImageToImageMetric);

  using typename Superclass::TransformType;
  using typename Superclass::TransformPointer;
  using typename Superclass::TransformJacobianType;
  using typename Superclass::InterpolatorType;
  using typename Superclass::MeasureType;
  using typename Superclass::DerivativeType;
  using typename Superclass::ParametersType;
  using typename Superclass::FixedImageType;
  using typename Superclass::MovingImageType;
  using typename Superclass::FixedImageConstPointer;
  using MovingImageCosntPointer = typename Superclass::MovingImageConstPointer;

  using FixedImageIndexType = typename FixedImageType::IndexType;
  using FixedImageIndexValueType = typename FixedImageIndexType::IndexValueType;
  using MovingImageIndexType = typename MovingImageType::IndexType;
  using FixedImagePointType = typename TransformType::InputPointType;
  using MovingImagePointType = typename TransformType::OutputPointType;
 
  using KernelFunctionType = KernelFunctionBase<double>;

  static constexpr unsigned int MovingImageDimension = MovingImageType::ImageDimension;

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

  MeasureType
  GetValue(const ParametersType & parameters) const override;

  void
  GetValueAndDerivative(const ParametersType & parameters,
                        MeasureType &          value,
                        DerivativeType &       derivative) const override;

  void
  SetNumberOfSpatialSamples(unsigned int num);

  itkGetConstReferenceMacro(NumberOfSpatialSamples, unsigned int);

  itkSetClampMacro(MovingImageStandardDeviation,
                   double,
                   NumericTraits<double>::NonpositiveMin(),
                   NumericTraits<double>::max());
  itkGetConstReferenceMacro(MovingImageStandardDeviation, double);

  itkSetClampMacro(FixedImageStandardDeviation,
                   double,
                   NumericTraits<double>::NonpositiveMin(),
                   NumericTraits<double>::max());
  itkGetConstMacro(FixedImageStandardDeviation, double);

  itkSetObjectMacro(KernelFunction, KernelFunctionType);
  itkGetModifiableObjectMacro(KernelFunction, KernelFunctionType);
 
 
protected:
  MutualInformationImageToImageMetric();
  ~MutualInformationImageToImageMetric() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;
 
private:
  class SpatialSample
  {
  public:
    SpatialSample() { FixedImagePointValue.Fill(0.0); }
    ~SpatialSample() = default;
 
    FixedImagePointType FixedImagePointValue;
    double              FixedImageValue{ 0.0 };
    double              MovingImageValue{ 0.0 };
  };

  using SpatialSampleContainer = std::vector<SpatialSample>;

  mutable SpatialSampleContainer m_SampleA{};

  mutable SpatialSampleContainer m_SampleB{};
 
  unsigned int m_NumberOfSpatialSamples{};
  double       m_MovingImageStandardDeviation{};
  double       m_FixedImageStandardDeviation{};
  double       m_MinProbability{};
 
  typename KernelFunctionType::Pointer m_KernelFunction{};

  virtual void
  SampleFixedImageDomain(SpatialSampleContainer & samples) const;
 
  /*
   * Calculate derivatives of the image intensity at the specified point with respect to the transform parameters.
   *
   * \todo This should really be done by the mapper.
   *
   * \todo This is a temporary solution until this feature is implemented
   * in the mapper. This solution only works for any transform
   * that support ComputeJacobianWithRespectToParameters()
   */
  void
  CalculateDerivatives(const FixedImagePointType &, DerivativeType &, TransformJacobianType &) const;
 
  using typename Superclass::CoordinateRepresentationType;
  using DerivativeFunctionType = CentralDifferenceImageFunction<MovingImageType, CoordinateRepresentationType>;
 
  typename DerivativeFunctionType::Pointer m_DerivativeCalculator{};
};
} // end namespace itk
 
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkMutualInformationImageToImageMetric.hxx"
#endif
 
#endif