#include <itkNormalizedMutualInformationHistogramImageToImageMetric.h>

Inheritance diagram for itk::NormalizedMutualInformationHistogramImageToImageMetric< TFixedImage, TMovingImage >:

Collaboration diagram for itk::NormalizedMutualInformationHistogramImageToImageMetric< TFixedImage, TMovingImage >:

Public Types
using	ConstPointer = SmartPointer< const Self >

using	DerivativeType = typename Superclass::DerivativeType

using	FixedImageConstPointer = typename Superclass::FixedImageConstPointer

using	FixedImageType = typename Superclass::FixedImageType

using	GradientPixelType = typename Superclass::GradientPixelType

using	HistogramFrequencyType = typename HistogramType::AbsoluteFrequencyType

using	HistogramIteratorType = typename HistogramType::Iterator

using	HistogramMeasurementVectorType = typename HistogramType::MeasurementVectorType

using	HistogramType = typename Superclass::HistogramType

using	MeasureType = typename Superclass::MeasureType

using	MovingImageConstPointer = typename Superclass::MovingImageConstPointer

using	MovingImageType = typename Superclass::MovingImageType

using	Pointer = SmartPointer< Self >

using	RealType = typename Superclass::RealType

using	Self = NormalizedMutualInformationHistogramImageToImageMetric

using	Superclass = HistogramImageToImageMetric< TFixedImage, TMovingImage >

using	TransformJacobianType = typename Superclass::TransformJacobianType

using	TransformParametersType = typename Superclass::TransformParametersType

using	TransformPointer = typename Superclass::TransformPointer

using	TransformType = typename Superclass::TransformType

Public Types inherited from itk::HistogramImageToImageMetric< TFixedImage, TMovingImage >
using	ConstPointer = SmartPointer< const Self >

using	DerivativeType = typename Superclass::DerivativeType

using	FixedImageConstPointerType = typename Superclass::FixedImageConstPointer

using	FixedImagePixelType = typename Superclass::FixedImageType::PixelType

using	FixedImageType = typename Superclass::FixedImageType

using	GradientPixelType = typename Superclass::GradientPixelType

using	HistogramPointer = typename HistogramType::Pointer

using	HistogramSizeType = typename HistogramType::SizeType

using	HistogramType = Statistics::Histogram< double >

using	InputPointType = typename Superclass::InputPointType

using	MeasurementVectorType = typename HistogramType::MeasurementVectorType

using	MeasureType = typename Superclass::MeasureType

using	MovingImageConstPointerType = typename Superclass::MovingImageConstPointer

using	MovingImagePixelType = typename Superclass::MovingImageType::PixelType

using	MovingImageType = typename Superclass::MovingImageType

using	OutputPointType = typename Superclass::OutputPointType

using	Pointer = SmartPointer< Self >

using	RealType = typename Superclass::RealType

using	Self = HistogramImageToImageMetric

using	Superclass = ImageToImageMetric< TFixedImage, TMovingImage >

using	TransformJacobianType = typename Superclass::TransformJacobianType

using	TransformParametersType = typename Superclass::TransformParametersType

using	TransformPointer = typename Superclass::TransformPointer

using	TransformType = typename Superclass::TransformType

using	ScalesType = Array< double >

Public Types inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
using	ConstPointer = SmartPointer< const Self >

using	CoordinateRepresentationType = typename Superclass::ParametersValueType

using	DerivativeType = typename Superclass::DerivativeType

using	FixedImageConstPointer = typename FixedImageType::ConstPointer

using	FixedImageIndexContainer = std::vector< FixedImageIndexType >

using	FixedImageIndexType = typename FixedImageType::IndexType

using	FixedImageIndexValueType = typename FixedImageIndexType::IndexValueType

using	FixedImageMaskConstPointer = typename FixedImageMaskType::ConstPointer

using	FixedImageMaskPointer = typename FixedImageMaskType::Pointer

using	FixedImageMaskType = SpatialObject< Self::FixedImageDimension >

using	FixedImagePixelType = typename TFixedImage::PixelType

using	FixedImagePointType = typename TransformType::InputPointType

using	FixedImageRegionType = typename FixedImageType::RegionType

using	FixedImageType = TFixedImage

using	GradientImageFilterPointer = typename GradientImageFilterType::Pointer

using	GradientImageFilterType = GradientRecursiveGaussianImageFilter< MovingImageType, GradientImageType >

using	GradientImagePointer = SmartPointer< GradientImageType >

using	GradientImageType = Image< GradientPixelType, Self::MovingImageDimension >

using	GradientPixelType = CovariantVector< RealType, Self::MovingImageDimension >

using	InputPointType = typename TransformType::InputPointType

using	InterpolatorPointer = typename InterpolatorType::Pointer

using	InterpolatorType = InterpolateImageFunction< MovingImageType, CoordinateRepresentationType >

using	MeasureType = typename Superclass::MeasureType

using	MovingImageConstPointer = typename MovingImageType::ConstPointer

using	MovingImageIndexType = typename MovingImageType::IndexType

using	MovingImageMaskConstPointer = typename MovingImageMaskType::ConstPointer

using	MovingImageMaskPointer = typename MovingImageMaskType::Pointer

using	MovingImageMaskType = SpatialObject< Self::MovingImageDimension >

using	MovingImagePixelType = typename TMovingImage::PixelType

using	MovingImagePointType = typename TransformType::OutputPointType

using	MovingImageType = TMovingImage

using	OutputPointType = typename TransformType::OutputPointType

using	ParametersType = typename Superclass::ParametersType

using	Pointer = SmartPointer< Self >

using	RealType = typename NumericTraits< MovingImagePixelType >::RealType

using	Self = ImageToImageMetric

using	Superclass = SingleValuedCostFunction

using	TransformJacobianType = typename TransformType::JacobianType

using	TransformParametersType = typename TransformType::ParametersType

using	TransformPointer = typename TransformType::Pointer

using	TransformType = Transform< CoordinateRepresentationType, Self::MovingImageDimension, Self::FixedImageDimension >

using	MultiThreaderType = MultiThreaderBase

Public Types inherited from itk::SingleValuedCostFunction
using	ConstPointer = SmartPointer< const Self >

using	DerivativeType = Array< ParametersValueType >

using	MeasureType = double

using	ParametersType = Superclass::ParametersType

using	ParametersValueType = Superclass::ParametersValueType

using	Pointer = SmartPointer< Self >

using	Self = SingleValuedCostFunction

using	Superclass = CostFunction

Public Types inherited from itk::CostFunctionTemplate< TInternalComputationValueType >
using	ConstPointer = SmartPointer< const Self >

using	ParametersType = OptimizerParameters< TInternalComputationValueType >

using	ParametersValueType = TInternalComputationValueType

using	Pointer = SmartPointer< Self >

using	Self = CostFunctionTemplate

using	Superclass = Object

Public Types inherited from itk::Object
using	ConstPointer = SmartPointer< const Self >

using	Pointer = SmartPointer< Self >

using	Self = Object

using	Superclass = LightObject

Public Types inherited from itk::LightObject
using	ConstPointer = SmartPointer< const Self >

using	Pointer = SmartPointer< Self >

using	Self = LightObject

Public Member Functions
virtual ::itk::LightObject::Pointer	CreateAnother () const

virtual const char *	GetNameOfClass () const

Public Member Functions inherited from itk::HistogramImageToImageMetric< TFixedImage, TMovingImage >
virtual const HistogramSizeType &	GetHistogramSize () const

void	Initialize () override

virtual void	SetHistogramSize (HistogramSizeType _arg)

void	SetTransform (TransformType *transform) override

virtual void	SetUpperBoundIncreaseFactor (double _arg)

virtual double	GetUpperBoundIncreaseFactor () const

virtual void	SetPaddingValue (FixedImagePixelType _arg)

virtual const FixedImagePixelType &	GetPaddingValue () const

virtual const HistogramPointer &	GetHistogram () const

virtual void	SetUsePaddingValue (bool _arg)

virtual bool	GetUsePaddingValue () const

virtual void	SetDerivativeStepLength (double _arg)

virtual double	GetDerivativeStepLength () const

virtual void	SetDerivativeStepLengthScales (ScalesType _arg)

virtual const ScalesType &	GetDerivativeStepLengthScales () const

MeasureType	GetValue (const TransformParametersType &parameters) const override

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

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

void	SetLowerBound (const MeasurementVectorType &bounds)

const MeasurementVectorType &	GetLowerBound () const

void	SetUpperBound (const MeasurementVectorType &bounds)

const MeasurementVectorType &	GetUpperBound () const

Public Member Functions inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
virtual void	SetFixedImage (const FixedImageType *_arg)

virtual const FixedImageType *	GetFixedImage () const

virtual void	SetMovingImage (const MovingImageType *_arg)

virtual const MovingImageType *	GetMovingImage () const

virtual void	SetTransform (TransformType *_arg)

virtual TransformType *	GetModifiableTransform ()

virtual const TransformType *	GetTransform () const

virtual void	SetInterpolator (InterpolatorType *_arg)

virtual InterpolatorType *	GetModifiableInterpolator ()

virtual const InterpolatorType *	GetInterpolator () const

SizeValueType	GetNumberOfMovingImageSamples ()

virtual const SizeValueType &	GetNumberOfPixelsCounted () const

virtual void	SetFixedImageRegion (const FixedImageRegionType reg)

virtual const FixedImageRegionType &	GetFixedImageRegion () const

virtual void	SetMovingImageMask (MovingImageMaskType *_arg)

virtual void	SetMovingImageMask (const MovingImageMaskType *_arg)

virtual const MovingImageMaskType *	GetMovingImageMask () const

virtual void	SetFixedImageMask (FixedImageMaskType *_arg)

virtual void	SetFixedImageMask (const FixedImageMaskType *_arg)

virtual const FixedImageMaskType *	GetFixedImageMask () const

void	SetFixedImageIndexes (const FixedImageIndexContainer &indexes)

void	SetUseFixedImageIndexes (bool useIndexes)

virtual const bool &	GetUseFixedImageIndexes () const

void	SetNumberOfWorkUnits (ThreadIdType numberOfThreads)

virtual const ThreadIdType &	GetNumberOfWorkUnits () const

virtual void	SetComputeGradient (bool _arg)

virtual const bool &	GetComputeGradient () const

virtual void	ComputeGradientOn ()

virtual void	ComputeGradientOff ()

virtual void	ComputeGradient ()

virtual GradientImageType *	GetModifiableGradientImage ()

virtual const GradientImageType *	GetGradientImage () const

void	SetTransformParameters (const ParametersType &parameters) const

unsigned int	GetNumberOfParameters () const override

virtual void	MultiThreadingInitialize ()

virtual void	SetNumberOfFixedImageSamples (SizeValueType numSamples)

virtual const SizeValueType &	GetNumberOfFixedImageSamples () const

void	SetNumberOfSpatialSamples (SizeValueType num)

SizeValueType	GetNumberOfSpatialSamples ()

void	SetFixedImageSamplesIntensityThreshold (const FixedImagePixelType &thresh)

virtual const FixedImagePixelType &	GetFixedImageSamplesIntensityThreshold () const

void	SetUseFixedImageSamplesIntensityThreshold (bool useThresh)

virtual const bool &	GetUseFixedImageSamplesIntensityThreshold () const

void	SetUseAllPixels (bool useAllPixels)

void	UseAllPixelsOn ()

void	UseAllPixelsOff ()

virtual const bool &	GetUseAllPixels () const

void	SetUseSequentialSampling (bool useSequential)

virtual const bool &	GetUseSequentialSampling () const

void	ReinitializeSeed ()

void	ReinitializeSeed (int seed)

virtual void	SetUseCachingOfBSplineWeights (bool _arg)

virtual const bool &	GetUseCachingOfBSplineWeights () const

virtual void	UseCachingOfBSplineWeightsOn ()

virtual void	UseCachingOfBSplineWeightsOff ()

virtual MultiThreaderType *	GetModifiableThreader ()

virtual const MultiThreaderType *	GetThreader () const

const TransformPointer *	GetThreaderTransform ()

Public Member Functions inherited from itk::SingleValuedCostFunction
virtual void	GetDerivative (const ParametersType &parameters, DerivativeType &derivative) const =0

virtual MeasureType	GetValue (const ParametersType &parameters) const =0

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

Public Member Functions inherited from itk::Object
unsigned long	AddObserver (const EventObject &event, Command *)

unsigned long	AddObserver (const EventObject &event, Command *) const

unsigned long	AddObserver (const EventObject &event, std::function< void(const EventObject &)> function) const

virtual void	DebugOff () const

virtual void	DebugOn () const

Command *	GetCommand (unsigned long tag)

bool	GetDebug () const

MetaDataDictionary &	GetMetaDataDictionary ()

const MetaDataDictionary &	GetMetaDataDictionary () const

virtual ModifiedTimeType	GetMTime () const

virtual const TimeStamp &	GetTimeStamp () const

bool	HasObserver (const EventObject &event) const

void	InvokeEvent (const EventObject &)

void	InvokeEvent (const EventObject &) const

virtual void	Modified () const

void	Register () const override

void	RemoveAllObservers ()

void	RemoveObserver (unsigned long tag)

void	SetDebug (bool debugFlag) const

void	SetReferenceCount (int) override

void	UnRegister () const noexcept override

void	SetMetaDataDictionary (const MetaDataDictionary &rhs)

void	SetMetaDataDictionary (MetaDataDictionary &&rrhs)

virtual void	SetObjectName (std::string _arg)

virtual const std::string &	GetObjectName () const

Public Member Functions inherited from itk::LightObject
Pointer	Clone () const

virtual void	Delete ()

virtual int	GetReferenceCount () const

void	Print (std::ostream &os, Indent indent=0) const

Static Public Member Functions
static Pointer	New ()

Static Public Member Functions inherited from itk::Object
static bool	GetGlobalWarningDisplay ()

static void	GlobalWarningDisplayOff ()

static void	GlobalWarningDisplayOn ()

static Pointer	New ()

static void	SetGlobalWarningDisplay (bool val)

Static Public Member Functions inherited from itk::LightObject
static void	BreakOnError ()

static Pointer	New ()

Protected Member Functions

	NormalizedMutualInformationHistogramImageToImageMetric ()=default

	~NormalizedMutualInformationHistogramImageToImageMetric () override=default

MeasureType	EvaluateMeasure (HistogramType &histogram) const override

Protected Member Functions inherited from itk::HistogramImageToImageMetric< TFixedImage, TMovingImage >
	HistogramImageToImageMetric ()

	~HistogramImageToImageMetric () override=default

void	ComputeHistogram (const TransformParametersType &parameters, HistogramType &histogram) const

void	ComputeHistogram (const TransformParametersType &parameters, unsigned int parameter, double step, HistogramType &histogram) const

void	CopyHistogram (HistogramType &target, HistogramType &source) const

void	PrintSelf (std::ostream &os, Indent indent) const override

Protected Member Functions inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
	ImageToImageMetric ()

	~ImageToImageMetric () override

void	PrintSelf (std::ostream &os, Indent indent) const override

virtual void	SampleFixedImageRegion (FixedImageSampleContainer &samples) const

virtual void	SampleFixedImageIndexes (FixedImageSampleContainer &samples) const

virtual void	SampleFullFixedImageRegion (FixedImageSampleContainer &samples) const

virtual void	PreComputeTransformValues ()

virtual void	TransformPoint (unsigned int sampleNumber, MovingImagePointType &mappedPoint, bool &sampleOk, double &movingImageValue, ThreadIdType threadId) const

virtual void	TransformPointWithDerivatives (unsigned int sampleNumber, MovingImagePointType &mappedPoint, bool &sampleOk, double &movingImageValue, ImageDerivativesType &movingImageGradient, ThreadIdType threadId) const

virtual void	ComputeImageDerivatives (const MovingImagePointType &mappedPoint, ImageDerivativesType &gradient, ThreadIdType threadId) const

void	GetValueMultiThreadedInitiate () const

void	GetValueMultiThreadedPostProcessInitiate () const

virtual void	GetValueThread (ThreadIdType threadId) const

virtual void	GetValueThreadPreProcess (ThreadIdType, bool) const

virtual bool	GetValueThreadProcessSample (ThreadIdType, SizeValueType, const MovingImagePointType &, double) const

virtual void	GetValueThreadPostProcess (ThreadIdType, bool) const

void	GetValueAndDerivativeMultiThreadedInitiate () const

void	GetValueAndDerivativeMultiThreadedPostProcessInitiate () const

virtual void	GetValueAndDerivativeThread (ThreadIdType threadId) const

virtual void	GetValueAndDerivativeThreadPreProcess (ThreadIdType, bool) const

virtual bool	GetValueAndDerivativeThreadProcessSample (ThreadIdType, SizeValueType, const MovingImagePointType &, double, const ImageDerivativesType &) const

virtual void	GetValueAndDerivativeThreadPostProcess (ThreadIdType, bool) const

virtual void	SynchronizeTransforms () const

Protected Member Functions inherited from itk::SingleValuedCostFunction
	SingleValuedCostFunction ()=default

	~SingleValuedCostFunction () override

Protected Member Functions inherited from itk::CostFunctionTemplate< TInternalComputationValueType >
	CostFunctionTemplate ()=default

	~CostFunctionTemplate () override=default

Protected Member Functions inherited from itk::Object
	Object ()

	~Object () override

bool	PrintObservers (std::ostream &os, Indent indent) const

virtual void	SetTimeStamp (const TimeStamp &timeStamp)

Protected Member Functions inherited from itk::LightObject
virtual LightObject::Pointer	InternalClone () const

	LightObject ()

virtual void	PrintHeader (std::ostream &os, Indent indent) const

virtual void	PrintTrailer (std::ostream &os, Indent indent) const

virtual	~LightObject ()

Additional Inherited Members
Static Public Attributes inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
static constexpr unsigned int	FixedImageDimension = TFixedImage::ImageDimension

static constexpr unsigned int	MovingImageDimension = TMovingImage::ImageDimension

Protected Types inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
using	FixedImageSampleContainer = std::vector< FixedImageSamplePoint >

using	BSplineTransformType = BSplineBaseTransform< CoordinateRepresentationType, FixedImageType::ImageDimension, Self::DeformationSplineOrder >

using	BSplineTransformWeightsType = typename BSplineTransformType::WeightsType

using	WeightsValueType = typename BSplineTransformWeightsType::ValueType

using	BSplineTransformWeightsArrayType = Array2D< WeightsValueType >

using	BSplineTransformIndexArrayType = typename BSplineTransformType::ParameterIndexArrayType

using	IndexValueType = typename BSplineTransformIndexArrayType::ValueType

using	BSplineTransformIndicesArrayType = Array2D< IndexValueType >

using	MovingImagePointArrayType = std::vector< MovingImagePointType >

using	BooleanArrayType = std::vector< bool >

using	BSplineParametersOffsetType = FixedArray< SizeValueType, FixedImageType::ImageDimension >

using	BSplineInterpolatorType = BSplineInterpolateImageFunction< MovingImageType, CoordinateRepresentationType >

using	DerivativeFunctionType = CentralDifferenceImageFunction< MovingImageType, CoordinateRepresentationType >

using	ImageDerivativesType = CovariantVector< double, Self::MovingImageDimension >

Static Protected Member Functions inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
static ITK_THREAD_RETURN_FUNCTION_CALL_CONVENTION	GetValueMultiThreaded (void *workunitInfoAsVoid)

static ITK_THREAD_RETURN_FUNCTION_CALL_CONVENTION	GetValueMultiThreadedPostProcess (void *workunitInfoAsVoid)

static ITK_THREAD_RETURN_FUNCTION_CALL_CONVENTION	GetValueAndDerivativeMultiThreaded (void *workunitInfoAsVoid)

static ITK_THREAD_RETURN_FUNCTION_CALL_CONVENTION	GetValueAndDerivativeMultiThreadedPostProcess (void *workunitInfoAsVoid)

Protected Attributes inherited from itk::HistogramImageToImageMetric< TFixedImage, TMovingImage >
HistogramSizeType	m_HistogramSize

MeasurementVectorType	m_LowerBound

MeasurementVectorType	m_UpperBound

double	m_UpperBoundIncreaseFactor

bool	m_LowerBoundSetByUser

bool	m_UpperBoundSetByUser

Protected Attributes inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
bool	m_UseFixedImageIndexes { false }

FixedImageIndexContainer	m_FixedImageIndexes

bool	m_UseFixedImageSamplesIntensityThreshold { false }

FixedImagePixelType	m_FixedImageSamplesIntensityThreshold

FixedImageSampleContainer	m_FixedImageSamples

SizeValueType	m_NumberOfParameters { 0 }

SizeValueType	m_NumberOfFixedImageSamples { 50000 }

SizeValueType	m_NumberOfPixelsCounted { 0 }

FixedImageConstPointer	m_FixedImage

MovingImageConstPointer	m_MovingImage

TransformPointer	m_Transform

TransformPointer *	m_ThreaderTransform

InterpolatorPointer	m_Interpolator

bool	m_ComputeGradient { true }

GradientImagePointer	m_GradientImage

FixedImageMaskConstPointer	m_FixedImageMask

MovingImageMaskConstPointer	m_MovingImageMask

ThreadIdType	m_NumberOfWorkUnits { 1 }

bool	m_UseAllPixels { false }

bool	m_UseSequentialSampling { false }

bool	m_ReseedIterator { false }

int	m_RandomSeed

bool	m_TransformIsBSpline { false }

SizeValueType	m_NumBSplineWeights { 0 }

BSplineTransformType::Pointer	m_BSplineTransform

BSplineTransformWeightsArrayType	m_BSplineTransformWeightsArray

BSplineTransformIndicesArrayType	m_BSplineTransformIndicesArray

MovingImagePointArrayType	m_BSplinePreTransformPointsArray

BooleanArrayType	m_WithinBSplineSupportRegionArray

BSplineParametersOffsetType	m_BSplineParametersOffset

bool	m_UseCachingOfBSplineWeights { true }

BSplineTransformWeightsType	m_BSplineTransformWeights

BSplineTransformIndexArrayType	m_BSplineTransformIndices

BSplineTransformWeightsType *	m_ThreaderBSplineTransformWeights

BSplineTransformIndexArrayType *	m_ThreaderBSplineTransformIndices

bool	m_InterpolatorIsBSpline { false }

BSplineInterpolatorType::Pointer	m_BSplineInterpolator

DerivativeFunctionType::Pointer	m_DerivativeCalculator

MultiThreaderType::Pointer	m_Threader

ConstantPointerWrapper *	m_ConstSelfWrapper

unsigned int *	m_ThreaderNumberOfMovingImageSamples { nullptr }

bool	m_WithinThreadPreProcess { false }

bool	m_WithinThreadPostProcess { false }

Protected Attributes inherited from itk::LightObject
std::atomic< int >	m_ReferenceCount

Static Protected Attributes inherited from itk::ImageToImageMetric< TFixedImage, TMovingImage >
static constexpr unsigned int	DeformationSplineOrder = 3

Detailed Description

template<typename TFixedImage, typename TMovingImage>
class itk::NormalizedMutualInformationHistogramImageToImageMetric< TFixedImage, TMovingImage >

Computes normalized mutual information between two images to be registered using the histograms of the intensities in the images.

The type of Normalize Mutual Information implemented in this class is given by the equation

$\frac{ H(A) + H(B) }{ H(A,B) }$

Where $ H(A) $ is the entropy of image $ A $, $ H(B) $ is the entropy of image $ B $, and $ H(A,B) $ is the joing entropy of images $ A $ and $ B $.

Details of this implementation can be found in the book "Medical Image Registration" by Hajnal, Hill and Hawkes. The book is available online at http://books.google.com/books?id=2dtQNsk-qBQC The implementation of this class corresponds to equation (30) in Chapter 3 of this book. Note that by slightly changing this class it will be trivial to compute the Normalized Mutual Information measures defined in equations (28) and (29) of the same book.

This class is templated over the type of the fixed and moving images to be compared.

Examples: Examples/RegistrationITKv4/ImageRegistration14.cxx, and Examples/RegistrationITKv4/ImageRegistration15.cxx.

Definition at line 52 of file itkNormalizedMutualInformationHistogramImageToImageMetric.h.