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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkConditionalConstIterator.h,v $
  Language:  C++
  Date:      $Date: 2006/03/18 20:14:38 $
  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 __itkConditionalConstIterator_h
#define __itkConditionalConstIterator_h

#include "itkIndex.h"

namespace itk
{

/** \class ConditionalConstIterator
 * \brief ConditionalConstIterator is a base class for other iterators where
 * membership in the set of output pixels is "conditional" upon some
 * property, calculation, etc. For example, a threshold iterator might
 * walk a region and return only those pixels which meet a minimum
 * intensity condition.
 *
 * This class is the const version of the ConditionalIterator
 * for this reason it doesn't support the Set() method.
 * 
 * \ingroup ImageIterators
 */
template<class TImage>
class ConditionalConstIterator {
public:
  /** Standard class typedefs. */
  typedef ConditionalConstIterator Self;
  
  /** Dimension of the image the iterator walks.  This constant is needed so 
   * that functions that are templated over image iterator type (as opposed to
   * being templated over pixel type and dimension) can have compile time
   * access to the dimension of the image that the iterator walks. */
  itkStaticConstMacro(NDimension, unsigned int, TImage::ImageDimension);

  /** Index typedef support. */
  typedef typename TImage::IndexType  IndexType;

  /** Size typedef support. */
  typedef typename TImage::SizeType    SizeType;

  /** Region typedef support. */
  typedef typename TImage::RegionType    RegionType;

  /** Image typedef support. */
  typedef TImage   ImageType;

  /** Internal Pixel Type */
  typedef typename TImage::InternalPixelType   InternalPixelType;

  /** External Pixel Type */
  typedef typename TImage::PixelType   PixelType;

  /** Compute whether the index of interest should be included in the flood */
  virtual bool IsPixelIncluded(const IndexType & index) const = 0;
  
  /** operator= is provided to make sure the handle to the image is properly
   * reference counted. */
  Self &operator=(const Self& it)
    {
    m_Image = it.m_Image;     // copy the smart pointer
    m_Region = it.m_Region;   // copy the region
    return *this;
    }
  
  /** Get the dimension (size) of the index. */
  static unsigned int GetIteratorDimension() 
    {return TImage::ImageDimension;}

  /** Get the index at the current iterator location. */
  virtual const IndexType GetIndex() = 0;

  /** Get the pixel value at the current iterator location. */
  virtual const PixelType & Get(void) const = 0;
  
  /** Is the iterator at the end of the region? */
  virtual bool IsAtEnd() = 0;

  /** Walk forward one index. */
  virtual void operator++() = 0;
  
  /** Constructor */
  ConditionalConstIterator();

  /** Destructor */
  virtual ~ConditionalConstIterator();

protected: //made protected so other iterators can access 
  /** Smart pointer to the source image. */
  //SmartPointer<const ImageType> m_Image;
  typename ImageType::ConstWeakPointer m_Image;

  /** Region type to iterate over. */
  RegionType m_Region;

  /** Is the iterator at the end of its walk? */
  bool m_IsAtEnd;
};

} // end namespace itk

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

#endif 
