/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkMeanSquaresImageToImageMetric2.h,v $
  Language:  C++
  Date:      $Date: 2003/09/10 14:28:35 $
  Version:   $Revision: 1.27 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef __itkMeanSquaresImageToImageMetric2_h
#define __itkMeanSquaresImageToImageMetric2_h

#include "itkImageToImageMetric.h"
#include "itkCovariantVector.h"
#include "itkPoint.h"
#include "itkBSplineDeformableTransform.h"
#include "itkCentralDifferenceImageFunction.h"


namespace itk
{
/** \class MeanSquaresImageToImageMetric2
 * \brief Computes similarity between two objects to be registered
 *
 * This Class is templated over the type of the fixed and moving
 * images to be compared.
 *
 * This metric computes the sum of squared differenced between pixels in
 * the moving image and pixels in the fixed image. The spatial correspondance 
 * between both images is established through a Transform. Pixel values are
 * taken from the Moving image. Their positions are mapped to the Fixed image
 * and result in general in non-grid position on it. Values at these non-grid
 * position of the Fixed image are interpolated using a user-selected Interpolator.
 *
 * The difference between this class and MeanSquaresImageToImageMetric is
 * that optimization have been added to improve performance when used
 * in registration with a BSplineDeformableTransform.
 *
 * \ingroup RegistrationMetrics
 */
template < class TFixedImage, class TMovingImage > 
class ITK_EXPORT MeanSquaresImageToImageMetric2 : 
    public ImageToImageMetric< TFixedImage, TMovingImage>
{
public:

  /** Standard class typedefs. */
  typedef MeanSquaresImageToImageMetric2    Self;
  typedef ImageToImageMetric<TFixedImage, TMovingImage >  Superclass;

  typedef SmartPointer<Self>         Pointer;
  typedef SmartPointer<const Self>   ConstPointer;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);
 
  /** Run-time type information (and related methods). */
  itkTypeMacro(MeanSquaresImageToImageMetric2, ImageToImageMetric);

 
  /** Types transferred from the base class */
  typedef typename Superclass::RealType                 RealType;
  typedef typename Superclass::TransformType            TransformType;
  typedef typename Superclass::TransformPointer         TransformPointer;
  typedef typename Superclass::TransformParametersType  TransformParametersType;
  typedef typename Superclass::TransformJacobianType    TransformJacobianType;
  typedef typename Superclass::GradientPixelType        GradientPixelType;

  typedef typename Superclass::MeasureType              MeasureType;
  typedef typename Superclass::DerivativeType           DerivativeType;
  typedef typename Superclass::FixedImageType           FixedImageType;
  typedef typename Superclass::MovingImageType          MovingImageType;
  typedef typename Superclass::FixedImageConstPointer   FixedImageConstPointer;
  typedef typename Superclass::MovingImageConstPointer  MovingImageConstPointer;

  typedef typename Superclass::CoordinateRepresentationType 
      CoordinateRepresentationType;

  /** Initialize the metric */
  virtual void Initialize(void) throw ( ExceptionObject );

  /** Get the derivatives of the match measure. */
  void GetDerivative( const TransformParametersType & parameters,
                      DerivativeType & derivative ) const;

  /**  Get the value for single valued optimizers. */
  MeasureType GetValue( const TransformParametersType & parameters ) const;

  /**  Get value and derivatives for multiple valued optimizers. */
  void GetValueAndDerivative( const TransformParametersType & parameters,
                              MeasureType& Value, DerivativeType& Derivative ) const;

protected:
  MeanSquaresImageToImageMetric2();
  virtual ~MeanSquaresImageToImageMetric2() {};

private:
  MeanSquaresImageToImageMetric2(const Self&); //purposely not implemented
  void operator=(const Self&); //purposely not implemented

  /** Boolean to indicate if the transform is BSpline deformable. */
  bool m_TransformIsBSpline;

  /** 
   * Enum of the deformabtion field spline order. 
   */
  enum { DeformationSplineOrder = 3 };

  /**
   * Typedefs for the BSplineDeformableTransform.
   */
  typedef BSplineDeformableTransform<
    CoordinateRepresentationType,
    ::itk::GetImageDimension<FixedImageType>::ImageDimension,
    DeformationSplineOrder> BSplineTransformType;
  typedef typename BSplineTransformType::WeightsType 
  BSplineTransformWeightsType;
  typedef typename BSplineTransformType::ParameterIndexArrayType 
  BSplineTransformIndexArrayType;

  /**
   * Variables used when transform is of type BSpline deformable.
   */
  typename BSplineTransformType::Pointer m_BSplineTransform;

  /** Typedefs for using central difference calculator. */
  typedef CentralDifferenceImageFunction<MovingImageType,
                                         CoordinateRepresentationType> DerivativeFunctionType;

  /** Pointer to central difference calculator. */
  typename DerivativeFunctionType::Pointer m_DerivativeCalculator;


};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkMeanSquaresImageToImageMetric2.txx"
#endif

#endif