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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkGeodesicActiveContourLevelSetFunction.h,v $
  Language:  C++
  Date:      $Date: 2003/09/10 14:28:30 $
  Version:   $Revision: 1.9 $

  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 __itkGeodesicActiveContourLevelSetFunction_h_
#define __itkGeodesicActiveContourLevelSetFunction_h_

#include "itkSegmentationLevelSetFunction.h"

namespace itk {

/** \class GeodesicActiveContourLevelSetFunction
 *    
 * \brief This function is used in GeodesicActiveContourLevelSetImageFilter to
 * segment structures in an image based on a user supplied edge potential map.
 *
 * \par IMPORTANT
 * The LevelSetFunction class contain additional information necessary
 * to gain full understanding of how to use this function.
 *
 * GeodesicActiveContourLevelSetFunction is a subclass of the generic LevelSetFunction.
 * It is used to segment structures in an image based on a user supplied 
 * edge potential map \f$ g(I) \f$, which
 * has values close to zero in regions near edges (or high image gradient) and values
 * close to one in regions with relatively constant intensity. Typically, the edge
 * potential map is a function of the gradient, for example:
 *
 * \f[ g(I) = 1 / ( 1 + | (\nabla * G)(I)| ) \f]
 * \f[ g(I) = \exp^{-|(\nabla * G)(I)|} \f]
 * 
 * where \f$ I \f$ is image intensity and
 * \f$ (\nabla * G) \f$ is the derivative of Gaussian operator. 
 *
 * The edge potential image is set via the SetFeatureImage() method.
 *
 * In this function both the propagation term \f$ P(\mathbf{x}) \f$
 * and the curvature spatial modifier term \f$ Z(\mathbf{x}) \f$ are taken directly
 * from the edge potential image such that:
 *
 * \f[ P(\mathbf{x}) = g(\mathbf{x}) \f]
 * \f[ Z(\mathbf{x}) = g(\mathbf{x}) \f]
 *
 * An advection term \f$ \mathbf{A}(\mathbf{x}) \f$ is constructed
 * from the negative gradient of the edge potential image. 
 *
 * \f[ \mathbf{A}(\matbf{x}) = -\nabla g(\mathbf{x}) \f]
 *
 * This term behaves like a doublet attracting the contour to the edges.
 * 
 * This implementation is based on:
 * "Geodesic Active Contours",
 * V. Caselles, R. Kimmel and G. Sapiro.
 * International Journal on Computer Vision,
 * Vol 22, No. 1, pp 61-97, 1997
 *
 * \sa LevelSetFunction
 * \sa SegmentationLevelSetImageFunction
 * \sa GeodesicActiveContourLevelSetImageFilter
 *
 * \ingroup FiniteDifferenceFunctions
 */
template <class TImageType, class TFeatureImageType = TImageType>
class ITK_EXPORT GeodesicActiveContourLevelSetFunction
  : public SegmentationLevelSetFunction<TImageType, TFeatureImageType>
{
public:
  /** Standard class typedefs. */
  typedef GeodesicActiveContourLevelSetFunction Self;
  typedef SegmentationLevelSetFunction<TImageType, TFeatureImageType> Superclass;
  typedef SmartPointer<Self> Pointer;
  typedef SmartPointer<const Self> ConstPointer;
  typedef TFeatureImageType FeatureImageType;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Run-time type information (and related methods) */
  itkTypeMacro( GeodesicActiveContourLevelSetFunction, SegmentationLevelSetFunction );

  /** Extract some parameters from the superclass. */
  typedef typename Superclass::ImageType ImageType;
  typedef typename Superclass::NeighborhoodType NeighborhoodType;
  typedef typename Superclass::ScalarValueType ScalarValueType;
  typedef typename Superclass::FeatureScalarType FeatureScalarType;
  typedef typename Superclass::RadiusType RadiusType;
  typedef typename Superclass::FloatOffsetType FloatOffsetType;
  typedef typename Superclass::VectorImageType VectorImageType;
  typedef typename Superclass::GlobalDataStruct GlobalDataStruct;

  /** Extract some parameters from the superclass. */
  itkStaticConstMacro(ImageDimension, unsigned int,
                      Superclass::ImageDimension);

  /** Compute speed image from feature image. */
  virtual void CalculateSpeedImage();

  /** Compute the advection field from feature image. */
  virtual void CalculateAdvectionImage();

  /** The curvature speed is same as the propagation speed. */
  virtual ScalarValueType CurvatureSpeed(const NeighborhoodType & neighborhood,
                                         const FloatOffsetType & offset, GlobalDataStruct *gd ) const
  { return PropagationSpeed( neighborhood, offset, gd ); }

  /** Set/Get the sigma for the Gaussian kernel used to compute the gradient
   * of the feature image needed for the advection term of the equation. */
  void SetDerivativeSigma( const double v )
  { m_DerivativeSigma = v; }
  double GetDerivativeSigma()
  { return m_DerivativeSigma; };

  virtual void Initialize(const RadiusType &r)
  {
    Superclass::Initialize(r);
    
    this->SetAdvectionWeight( NumericTraits<ScalarValueType>::One );
    this->SetPropagationWeight( NumericTraits<ScalarValueType>::One );
    this->SetCurvatureWeight( NumericTraits<ScalarValueType>::One );
  }
  
protected:
  GeodesicActiveContourLevelSetFunction()
  {
    this->SetAdvectionWeight( NumericTraits<ScalarValueType>::One );
    this->SetPropagationWeight( NumericTraits<ScalarValueType>::One );
    this->SetCurvatureWeight( NumericTraits<ScalarValueType>::One );

    m_DerivativeSigma = 1.0;
  }
  virtual ~GeodesicActiveContourLevelSetFunction() {}

  GeodesicActiveContourLevelSetFunction(const Self&); //purposely not implemented
  void operator=(const Self&); //purposely not implemented
  
  void PrintSelf(std::ostream& os, Indent indent) const
  {
    Superclass::PrintSelf(os, indent );
    os << indent << "DerivativeSigma: " << m_DerivativeSigma << std::endl;
  }

private:
  
  double m_DerivativeSigma;
  
};
  
} // end namespace itk

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

#endif
