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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkConstantBoundaryCondition.h,v $
  Language:  C++
  Date:      $Date: 2006/04/20 16:59:33 $
  Version:   $Revision: 1.19 $

  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 __itkConstantBoundaryCondition_h
#define __itkConstantBoundaryCondition_h
#include "itkNeighborhood.h"
#include "itkNumericTraits.h"
#include "itkImageBoundaryCondition.h"

namespace itk
{

/** \class ConstantBoundaryCondition
 * \brief This boundary condition returns a constant value for out-of-bounds
 * image pixels.
 * 
 * For example, invoking this function object with a constant value of zero
 * (the default) on each out-of-bounds element of a 7x5 iterator that masks a
 * region at an image corner 
 * (iterator is centered on the 2): 
 *
 *               * * * * * * * 
 *               * * * * * * *
 *               * * 1 2 3 4 5  (where * denotes pixels that lie 
 *               * * 3 3 5 5 6          outside of the image boundary)
 *               * * 4 4 6 7 8
 *
 * would produce the following neighborhood of values:
 *
 *               0 0 0 0 0 0 0
 *               0 0 0 0 0 0 0
 *               0 0 1 2 3 4 5
 *               0 0 3 3 5 5 6
 *               0 0 4 4 6 7 8
 *
 * 
 * \note If you are using an image with Array as the pixel type, you will need 
 * to set the constant explicitly with an array of the appropriate length. This 
 * is also true if your image type is a VectorImage.
 * 
 * \sa ImageBoundaryCondition
 *
 * \ingroup DataRepresentation
 * \ingroup ImageObjects
 */
template<class TImage>
class ITK_EXPORT ConstantBoundaryCondition
  : public ImageBoundaryCondition<TImage>
{
public:
  /** Self & superclass typedefs */ 
  typedef ConstantBoundaryCondition      Self;
  typedef ImageBoundaryCondition<TImage> Superclass;
  
  /** Extract information from the image type */
  typedef typename Superclass::PixelType        PixelType;
  typedef typename Superclass::PixelPointerType PixelPointerType;
  typedef typename Superclass::IndexType        IndexType;
  typedef typename Superclass::OffsetType       OffsetType;
  typedef typename Superclass::NeighborhoodType NeighborhoodType;
    
  typedef typename Superclass::NeighborhoodAccessorFunctorType 
                                 NeighborhoodAccessorFunctorType;

  /** Save the image dimension. */
  itkStaticConstMacro(ImageDimension, unsigned int,Superclass::ImageDimension);

  /** Default constructor. */
  ConstantBoundaryCondition()
    { m_Constant = NumericTraits<PixelType>::Zero; }

  /** Computes and returns appropriate out-of-bounds values from
   * neighborhood iterator data. */
  virtual PixelType operator()(const OffsetType&,
                               const OffsetType&,
                               const NeighborhoodType *) const
    { return m_Constant; }

  /** Computes and returns the appropriate pixel value from
   * neighborhood iterator data, using the functor. */
  virtual PixelType operator()(
      const OffsetType& ,
      const OffsetType& ,
      const NeighborhoodType *,
      const NeighborhoodAccessorFunctorType & ) const
    { return m_Constant; }
  
  /** Set the value of the constant. */
  void SetConstant(const PixelType &c)
    {  m_Constant = c; }

  /** Get the value of the constant. */
  const PixelType &GetConstant() const
    {  return m_Constant;  }
  
  /** Tell if the boundary condition can index to any location within
    * the associated iterator's neighborhood or if it has some limited
    * subset (such as none) that it relies upon. */
  bool RequiresCompleteNeighborhood() { return false; }

private:
  PixelType m_Constant;
};

} // end namespace itk

#endif
