itkAnisotropicFourthOrderLevelSetImageFilter.h

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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    itkAnisotropicFourthOrderLevelSetImageFilter.h
  Language:  C++
  Date:      $Date$
  Version:   $Revision$

  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 __itkAnisotropicFourthOrderLevelSetImageFilter_h
#define __itkAnisotropicFourthOrderLevelSetImageFilter_h

#include "itkLevelSetFunctionWithRefitTerm.h"
#include "itkSparseFieldFourthOrderLevelSetImageFilter.h"

namespace itk {

/**
 * \class AnisotropicFourthOrderLevelSetImageFilter
 *
 * \brief This class implements the 4th-order level set anisotropic diffusion
 * (smoothing) PDE.
 *
 * \par INPUT and OUTPUT
 * This is a volume to volume filter; however, it is meant to process (smooth)
 * surfaces. The input surface is an isosurface of the input volume. The
 * isosurface value to be processed can be set by calling SetIsoSurfaceValue
 * (default is 0). The output surface is the 0-isosurface of the output volume,
 * regardless of the input isosurface value. To visualize the input/output
 * surfaces to this filter a mesh extraction method such as marching cubes can
 * be used. 
 *
 * \par
 * The 4th-order level set PDE framework is proposed as an alternative to 2nd
 * order PDEs. By order we mean the order of differentiation of the level set
 * image function required to compute derivatives for updating the image. For
 * instance, the popular curvature flow uses 2nd-order derivatives of the level
 * set image; hence, it is a 2nd order PDE.
 *
 * \par
 * 2nd-order curvature flow can be used by itself to smooth surfaces as a
 * post-processing filter or it can be used with other PDE terms such as a
 * Canny edge term that attracts the surface to strong edges in a data
 * image. Curvature flow smoothes surfaces by making the surface move in the
 * direction that will decrease surface area.
 *
 * \par
 * The 4th-order PDE framework provides an improvement over curvature
 * flow. Instead of making the surface move to decrease surface area it makes
 * the surface move to decrease total curvature. Similar to curvature flow,
 * these PDEs can be used alone or in conjunction with data terms. The
 * 4th-order PDE framework is implemented in
 * SparseFieldFourthOrderLevelSetImageFilter. This filter class, which is
 * derived from that, uses the 4th-order PDE by itself to implement an
 * anisotropic surface smoothing algorithm. This is a feature preserving
 * surface processing algorithm that smoothes surfaces but will preserve
 * certain features (creases, edges, other sharp features) depending on the
 * NormalProcessConductanceParameter. 
 *
 * \par PARAMETERS
 * As mentioned before, the IsoSurfaceValue parameter chooses which isosurface
 * of the input to process. The MaxFilterIterations parameter determine the
 * number of iterations for which this filter will run. The more iterations,
 * the more smoothing. NormalProcessConductanceParameter controls the amount of
 * feature preservation. Its units are in curvature. Reasonable values for
 * almost all surface are in the range 0.1-0.25 . The shape of the surface
 * where the total curvature is above the value of this parameter will tend to
 * stay the same (be preserved) or even be sharpened. The lower the value, the more
 * feature preservation. Notice the difference between the number of iterations
 * parameter and the conductance parameter: for a given conductance parameter,
 * surface features with high enough curvature will be preserved even if the
 * number of iterations is set to be extremely large. 
 */
template <class TInputImage, class TOutputImage>
class ITK_EXPORT AnisotropicFourthOrderLevelSetImageFilter
  : public SparseFieldFourthOrderLevelSetImageFilter <TInputImage, TOutputImage>
{
public:
  /** Standard class typedefs */
  typedef AnisotropicFourthOrderLevelSetImageFilter                Self;
  typedef SparseFieldFourthOrderLevelSetImageFilter <TInputImage,
                                                     TOutputImage> Superclass;
  typedef SmartPointer<Self>                                       Pointer;
  typedef SmartPointer<const Self>                                 ConstPointer;

  /** Run-time type information (and related methods) */
  itkTypeMacro(AnisotropicFourthOrderLevelSetImageFilter,
               SparseFieldFourthOrderLevelSetImageFilter);

  /** Standard new macro */
  itkNewMacro( Self );

  /** The sparse image type used in LevelSetFunctionWithRefitTerm */
  typedef typename Superclass::SparseImageType SparseImageType;

  /** The level set function class with a refit term that forces the curvature
      of the moving front to match a prescribed curvature image. */
  typedef LevelSetFunctionWithRefitTerm <TOutputImage,SparseImageType> FunctionType;

  /** The radius type for the neighborhoods. */
  typedef typename FunctionType::RadiusType RadiusType;

  itkGetMacro(MaxFilterIteration,unsigned int);
  itkSetMacro(MaxFilterIteration,unsigned int);
  
protected:
  AnisotropicFourthOrderLevelSetImageFilter();
  ~AnisotropicFourthOrderLevelSetImageFilter() {};
  virtual void PrintSelf(std::ostream& os, Indent indent) const;
  
  /** This filter halts when the iteration count reaches the specified count. */
  virtual bool Halt()
    {
    if (this->GetElapsedIterations() == m_MaxFilterIteration)
      {
      return true;
      }
    else
      {
      return false;
      }
    }

private:
  AnisotropicFourthOrderLevelSetImageFilter(const Self&);
  //purposely not implemented
  void operator=(const Self&); //purposely not implemented

  /** The LevelSetFunctionWithRefitTerm object. */
  typename FunctionType::Pointer m_Function;

  /** The number of iterations for which this filter will run. */
  unsigned int m_MaxFilterIteration;

};

} // end namespace itk

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

#endif