itkMutualInformationImageToImageMetric.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
 *
 *         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 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_ASSIGN(MutualInformationImageToImageMetric);

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

  itkNewMacro(Self);

  itkTypeMacro(MutualInformationImageToImageMetric, ImageToImageMetric);

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

  void CalculateDerivatives(const FixedImagePointType &, DerivativeType &, TransformJacobianType &) const;

  using CoordinateRepresentationType = 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