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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkNthElementPixelAccessor.h,v $
  Language:  C++
  Date:      $Date: 2003/09/10 14:29:18 $
  Version:   $Revision: 1.10 $

  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 __itkNthElementPixelAccessor_h
#define __itkNthElementPixelAccessor_h

#include "itkMacro.h"

namespace itk
{

/** \class NthElementPixelAccessor
 * \brief Give access to the N-th of a Container type 
 *
 * This class is intended to be used as parameter of 
 * an ImageAdaptor to make a  Container appears as being
 * of scalar type T, showing only the N-th component.
 *
 * This class is templated over the container type.
 * Any container type that provides a method:
 * operator[]( unsigned int ) can be used here,
 * for example: itkPoint, itkVector, itkVectorContainer,
 *              and std::vector.
 *
 * For performance, no bound checking is performed during
 * access to the n-th element.
 *
 * \sa ImageAdaptor
 * \sa PixelAccessor
 *
 * \ingroup ImageAdaptors
 */

template < class T, class TContainer >
class ITK_EXPORT NthElementPixelAccessor
{
public:
  /** Standard class typedefs. */
  typedef   NthElementPixelAccessor        Self;

  /** that this class will exhibit */
  typedef T ExternalType;

  /** Internal typedef. It defines the internal real
   * representation of data */
  typedef   TContainer    InternalType;

  /** Write access to the NthElement component */
  inline void Set( InternalType & output, const ExternalType & input ) const 
    { output[m_ElementNumber] =  input; }

  /** Read access to the NthElement component */
  inline ExternalType Get( const InternalType & input ) const
    { return static_cast<ExternalType>( input[m_ElementNumber] ); }

  /** Get the element number to access in the container */
  unsigned int GetElementNumber(void) const
    { return m_ElementNumber; }

  /** Set the element number to access in the container */
  void SetElementNumber( unsigned int nth )
    { m_ElementNumber = nth; }

  /** operator!=. This is needed to convert a pixel accessor to a functor.
   * \sa AdaptImageFilter */
  bool operator!=(const Self& accessor) const
    {
      return (m_ElementNumber != accessor.m_ElementNumber);
    }

  /** Assignment operator */
  NthElementPixelAccessor & operator=( const NthElementPixelAccessor & accessor )
    {
    m_ElementNumber = accessor.m_ElementNumber;
    return *this;
    }
  
  /** Constructor */
  NthElementPixelAccessor()
    {
    m_ElementNumber = 0;
    }

private:
  // Identifier of the N-th element to be accessed
  unsigned int    m_ElementNumber;

};

  
}  // end namespace itk

#endif

