/*========================================================================= * * 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 itkSymmetricForcesDemonsRegistrationFunction_h #define itkSymmetricForcesDemonsRegistrationFunction_h #include "itkPDEDeformableRegistrationFunction.h" #include "itkPoint.h" #include "itkLinearInterpolateImageFunction.h" #include "itkCentralDifferenceImageFunction.h" #include namespace itk { /** * \class SymmetricForcesDemonsRegistrationFunction * * This class encapsulate the PDE which drives the demons registration * algorithm (formula (5) in J.-P. Thirions's paper "Fast Non-Rigid Matching of * 3D Medical Images", May 1995). It is used by SymmetricForcesDemonsRegistrationFilter * to compute the output displacement field which will map a moving image onto a * a fixed image. * * This class was contributed by Corinne Mattmann, ETH Zurich, Switzerland. * based on a variation of the DemonsRegistrationFunction. The basic modification * is to use equation (5) from Thirion's paper along with the modification for * avoiding large displacements when gradients have small values. * * Non-integer moving image values are obtained by using * interpolation. The default interpolator is of type * LinearInterpolateImageFunction. The user may set other * interpolators via method SetMovingImageInterpolator. Note that the input * interpolator must derive from baseclass InterpolateImageFunction. * * This class is templated over the fixed image type, moving image type, * and the displacement field type. * * \warning This filter assumes that the fixed image type, moving image type * and displacement field type all have the same number of dimensions. * * \sa SymmetricForcesDemonsRegistrationFilter * \sa DemonsRegistrationFilter * \sa DemonsRegistrationFunction * \ingroup FiniteDifferenceFunctions * \ingroup ITKPDEDeformableRegistration */ template class ITK_TEMPLATE_EXPORT SymmetricForcesDemonsRegistrationFunction : public PDEDeformableRegistrationFunction { public: ITK_DISALLOW_COPY_AND_MOVE(SymmetricForcesDemonsRegistrationFunction); /** Standard class type aliases. */ using Self = SymmetricForcesDemonsRegistrationFunction; using Superclass = PDEDeformableRegistrationFunction; using Pointer = SmartPointer; using ConstPointer = SmartPointer; /** Method for creation through the object factory. */ itkNewMacro(Self); /** \see LightObject::GetNameOfClass() */ itkOverrideGetNameOfClassMacro(SymmetricForcesDemonsRegistrationFunction); /** MovingImage image type. */ using typename Superclass::MovingImageType; using typename Superclass::MovingImagePointer; /** FixedImage image type. */ using typename Superclass::FixedImageType; using typename Superclass::FixedImagePointer; using IndexType = typename FixedImageType::IndexType; using SizeType = typename FixedImageType::SizeType; using SpacingType = typename FixedImageType::SpacingType; /** Deformation field type. */ using typename Superclass::DisplacementFieldType; using typename Superclass::DisplacementFieldTypePointer; /** Inherit some enums from the superclass. */ static constexpr unsigned int ImageDimension = Superclass::ImageDimension; /** Inherit some enums from the superclass. */ using typename Superclass::PixelType; using typename Superclass::RadiusType; using typename Superclass::NeighborhoodType; using typename Superclass::FloatOffsetType; using typename Superclass::TimeStepType; /** Interpolator type. */ using CoordRepType = double; using InterpolatorType = InterpolateImageFunction; using InterpolatorPointer = typename InterpolatorType::Pointer; using PointType = typename InterpolatorType::PointType; using DefaultInterpolatorType = LinearInterpolateImageFunction; /** Covariant vector type. */ using CovariantVectorType = CovariantVector; /** Gradient calculator type. */ using GradientCalculatorType = CentralDifferenceImageFunction; using GradientCalculatorPointer = typename GradientCalculatorType::Pointer; /** Set the moving image interpolator. */ void SetMovingImageInterpolator(InterpolatorType * ptr) { m_MovingImageInterpolator = ptr; } /** Get the moving image interpolator. */ InterpolatorType * GetMovingImageInterpolator() { return m_MovingImageInterpolator; } /** This class uses a constant timestep of 1. */ TimeStepType ComputeGlobalTimeStep(void * itkNotUsed(GlobalData)) const override { return m_TimeStep; } /** Return a pointer to a global data structure that is passed to * this object from the solver at each calculation. */ void * GetGlobalDataPointer() const override { auto * global = new GlobalDataStruct(); global->m_SumOfSquaredDifference = 0.0; global->m_NumberOfPixelsProcessed = 0L; global->m_SumOfSquaredChange = 0; return global; } /** Release memory for global data structure. * * Updates the metric and releases the per-thread-global data. */ void ReleaseGlobalDataPointer(void * gd) const override; /** Set the object's state before each iteration. */ void InitializeIteration() override; /** Compute update at a non boundary neighbourhood. * * Called by a finite difference solver image filter at each pixel that does not lie on a data set boundary. */ PixelType ComputeUpdate(const NeighborhoodType & it, void * gd, const FloatOffsetType & offset = FloatOffsetType(0.0)) override; /** Get the metric value. The metric value is the mean square difference * in intensity between the fixed image and transforming moving image * computed over the overlapping region between the two images. */ virtual double GetMetric() const { return m_Metric; } /** Get the rms change in displacement field. */ virtual const double & GetRMSChange() const { return m_RMSChange; } /** Set/Get the threshold below which the absolute difference of * intensity yields a match. When the intensities match between a * moving and fixed image pixel, the update vector (for that * iteration) will be the zero vector. Default is 0.001. */ virtual void SetIntensityDifferenceThreshold(double); virtual double GetIntensityDifferenceThreshold() const; protected: SymmetricForcesDemonsRegistrationFunction(); ~SymmetricForcesDemonsRegistrationFunction() override = default; void PrintSelf(std::ostream & os, Indent indent) const override; /** FixedImage image neighborhood iterator type. */ using FixedImageNeighborhoodIteratorType = ConstNeighborhoodIterator; /** A global data type for this class of equation. Used to store * iterators for the fixed image. */ struct GlobalDataStruct { double m_SumOfSquaredDifference; SizeValueType m_NumberOfPixelsProcessed; double m_SumOfSquaredChange; }; private: /** Cache fixed image information. */ SpacingType m_FixedImageSpacing{}; PointType m_FixedImageOrigin{}; double m_Normalizer{}; /** Function to compute derivatives of the fixed image. */ GradientCalculatorPointer m_FixedImageGradientCalculator{}; /** Function to interpolate the moving image. */ InterpolatorPointer m_MovingImageInterpolator{}; /** The global timestep. */ TimeStepType m_TimeStep{}; /** Threshold below which the denominator term is considered zero. */ double m_DenominatorThreshold{}; /** Threshold below which two intensity value are assumed to match. */ double m_IntensityDifferenceThreshold{}; /** The metric value is the mean square difference in intensity between * the fixed image and transforming moving image computed over the * the overlapping region between the two images. */ mutable double m_Metric{}; mutable double m_SumOfSquaredDifference{}; mutable SizeValueType m_NumberOfPixelsProcessed{}; mutable double m_RMSChange{}; mutable double m_SumOfSquaredChange{}; /** Mutex lock to protect modification to metric. */ mutable std::mutex m_MetricCalculationMutex{}; }; } // end namespace itk #ifndef ITK_MANUAL_INSTANTIATION # include "itkSymmetricForcesDemonsRegistrationFunction.hxx" #endif #endif