#ifndef __FPA__IMAGE__FUNCTORS__GRADIENTIMAGEFUNCTIONBASE__H__
#define __FPA__IMAGE__FUNCTORS__GRADIENTIMAGEFUNCTIONBASE__H__

#include <itkImageFunction.h>

namespace fpa
{
  namespace Image
  {
    namespace Functors
    {
      /**
       * Base class to compute values based on image gradients (vector).
       * It allows incremental computation of the gradient.
       */
      template< class _TGradient >
      class GradientImageFunctionBase
        : public itk::ImageFunction< _TGradient, typename _TGradient::PixelType::ValueType, typename _TGradient::PixelType::ValueType >
      {
      public:
        // Types from input arguments
        typedef _TGradient                     TGradient;
        typedef typename _TGradient::PixelType TVector;
        typedef typename TVector::ValueType    TScalar;
        itkStaticConstMacro( Dimension, unsigned int, _TGradient::ImageDimension );

        // Standard itk types
        typedef GradientImageFunctionBase                          Self;
        typedef itk::ImageFunction< _TGradient, TScalar, TScalar > Superclass;
        typedef itk::SmartPointer< Self >                          Pointer;
        typedef itk::SmartPointer< const Self >                    ConstPointer;

        // Types from base itk::ImageFunction
        typedef typename Superclass::InputType           TInput;
        typedef typename Superclass::OutputType          TOutput;
        typedef typename Superclass::PointType           TPoint;
        typedef typename Superclass::ContinuousIndexType TContIndex;
        typedef typename Superclass::IndexType           TIndex;

      public:
        itkTypeMacro( GradientImageFunctionBase, itkImageFunction );

      public:
        virtual void Prepare( ) const;
        virtual TOutput Evaluate( const TPoint& p ) const;
        virtual TOutput EvaluateAtIndex( const TIndex& i ) const;
        virtual TOutput EvaluateAtContinuousIndex( const TContIndex& i ) const;

      protected:
        GradientImageFunctionBase( );
        virtual ~GradientImageFunctionBase( );

        virtual TOutput _Evaluate( const TIndex& i ) const = 0;

      private:
        // Purposely not implemented.
        GradientImageFunctionBase( const Self& );
        void operator=( const Self& );
      };

    } // ecapseman

  } // ecapseman

} // ecapseman

#ifndef ITK_MANUAL_INSTANTIATION
#include <fpa/Image/Functors/GradientImageFunctionBase.hxx>
#endif // ITK_MANUAL_INSTANTIATION

#endif // __FPA__IMAGE__FUNCTORS__GRADIENTIMAGEFUNCTIONBASE__H__

// eof - $RCSfile$