itkContourExtractor2DImageFilter.h

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 *  Copyright Insight Software Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
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 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
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#ifndef __itkContourExtractor2DImageFilter_h
#define __itkContourExtractor2DImageFilter_h

#include "itkImageToPathFilter.h"
#include "itkPolyLineParametricPath.h"
#include "itkConceptChecking.h"
#include "itksys/hash_map.hxx"
#include "vcl_deque.h"
#include "vcl_list.h"

namespace itk
{
template< typename TInputImage >
class ContourExtractor2DImageFilter:
  public ImageToPathFilter< TInputImage, PolyLineParametricPath< 2 > >
{
public:
  itkStaticConstMacro(InputImageDimension, unsigned int,
                      TInputImage::ImageDimension);

  typedef TInputImage                 InputImageType;
  typedef PolyLineParametricPath< 2 > OutputPathType;

  typedef ContourExtractor2DImageFilter                       Self;
  typedef ImageToPathFilter< InputImageType, OutputPathType > Superclass;
  typedef SmartPointer< Self >                                Pointer;
  typedef SmartPointer< const Self >                          ConstPointer;

  itkNewMacro(Self);

  itkTypeMacro(ContourExtractor2DImageFilter, ImageToPathFilter);

  typedef typename InputImageType::Pointer        InputImagePointer;
  typedef typename InputImageType::PixelType      InputPixelType;
  typedef typename InputImageType::IndexType      InputIndexType;
  typedef typename InputImageType::OffsetType     InputOffsetType;
  typedef typename InputImageType::RegionType     InputRegionType;
  typedef typename OutputPathType::Pointer        OutputPathPointer;
  typedef typename OutputPathType::VertexType     VertexType;
  typedef typename OutputPathType::VertexListType VertexListType;

  typedef typename NumericTraits< InputPixelType >::RealType InputRealType;

  typedef typename VertexListType::ConstPointer
  VertexListConstPointer;
  itkSetMacro(ReverseContourOrientation, bool);
  itkGetConstReferenceMacro(ReverseContourOrientation, bool);
  itkBooleanMacro(ReverseContourOrientation);

  itkSetMacro(VertexConnectHighPixels, bool);
  itkGetConstReferenceMacro(VertexConnectHighPixels, bool);
  itkBooleanMacro(VertexConnectHighPixels);

  void SetRequestedRegion(const InputRegionType region);

  itkGetConstReferenceMacro(RequestedRegion, InputRegionType);
  void ClearRequestedRegion();

  itkSetMacro(ContourValue, InputRealType);
  itkGetConstReferenceMacro(ContourValue, InputRealType);

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( DimensionShouldBe2,
                   ( Concept::SameDimension< itkGetStaticConstMacro(InputImageDimension), 2 > ) );
  itkConceptMacro( InputPixelTypeComparable,
                   ( Concept::Comparable< InputPixelType > ) );
  itkConceptMacro( InputHasPixelTraitsCheck,
                   ( Concept::HasPixelTraits< InputPixelType > ) );
  itkConceptMacro( InputHasNumericTraitsCheck,
                   ( Concept::HasNumericTraits< InputPixelType > ) );
  // End concept checking
#endif

protected:

  ContourExtractor2DImageFilter();
  virtual ~ContourExtractor2DImageFilter();
  void PrintSelf(std::ostream & os, Indent indent) const;

  void GenerateData();

  virtual void GenerateInputRequestedRegion();

private:
  VertexType InterpolateContourPosition(InputPixelType fromValue,
                                        InputPixelType toValue,
                                        InputIndexType fromIndex,
                                        InputOffsetType toOffset);

  void AddSegment(const VertexType from, const VertexType to);

  void FillOutputs();

  ContourExtractor2DImageFilter(const Self &); //purposely not implemented
  void operator=(const Self &);                //purposely not implemented

  InputRealType   m_ContourValue;
  bool            m_ReverseContourOrientation;
  bool            m_VertexConnectHighPixels;
  bool            m_UseCustomRegion;
  InputRegionType m_RequestedRegion;
  unsigned int    m_NumberOfContoursCreated;

  // Represent each contour as deque of vertices to facilitate addition of
  // nodes at beginning or end. At the end of the processing, we will copy
  // the contour into a PolyLineParametricPath.
  // We subclass the deque to store an additional bit of information: an
  // identification number for each growing contour. We use this number so
  // that when it becomes necessary to merge two growing contours, we can
  // merge the newer one into the older one. This helps because then we can
  // guarantee that the output contour list is ordered from left to right,
  // top to bottom (in terms of the first pixel of the contour encountered
  // by the marching squares). Currently we make no guarantees that this
  // pixel is the first pixel in the contour list, just that the contours
  // are so ordered in the output. Ensuring this latter condition (first
  // pixel traversed = first pixel in contour) would be possible by either
  // changing the merging rules, which would make the contouring operation
  //slower, or by storing additional data as to which pixel was first.
  class ContourType:public vcl_deque< VertexType >
  {
public:
    unsigned int m_ContourNumber;
  };

  // Store all the growing contours in a list. We may need to delete contours
  // from anywhere in the sequence (when we merge them together), so we need to
  // use a list instead of a vector or similar.
  typedef vcl_list< ContourType >             ContourContainer;
  typedef typename ContourContainer::iterator ContourRef;

  // declare the hash function we are using for the hash_map.
  struct VertexHash {
    typedef typename VertexType::CoordRepType CoordinateType;
    inline SizeValueType operator()(const VertexType & k) const
    {
      // Xor the hashes of the vertices together, after multiplying the
      // first by some number, so that identical (x,y) vertex indices
      // don't all hash to the same bucket. This is a decent if not
      // optimal hash.
      const SizeValueType hashVertex1 = this->float_hash(k[0] * 0xbeef);
      const SizeValueType hashVertex2 = this->float_hash(k[1]);
      const SizeValueType hashValue = hashVertex1 ^ hashVertex2;

      return hashValue;
    }

    // Define hash function for floats. Based on method from
    // http://www.brpreiss.com/books/opus4/html/page217.html
    inline SizeValueType float_hash(const CoordinateType & k) const
    {
      if ( k == 0 )
        {
        return 0;
        }
      int            exponent;
      CoordinateType mantissa = vcl_frexp(k, &exponent);
      SizeValueType  value = static_cast< SizeValueType >( std::fabs(mantissa) );
      value = ( 2 * value - 1 ) * ~0U;
      return value;
    }
  };

  // We use a hash to associate the endpoints of each contour with the
  // contour itself. This makes it easy to look up which contour we should add
  // a new arc to.
  // We can't store the contours themselves in the hashtable because we
  // need to have two tables (one to hash from beginpoint -> contour and one
  // for endpoint -> contour), and sometimes will remove a contour from the
  // tables (if it has been closed or merged with another contour). So in the
  // hash table we store a reference to the contour. Because sometimes we will
  // need to merge contours, we need to be able to quickly remove contours
  // from our list when they have been merged into another. Thus, we store
  // an iterator pointing to the contour in the list.

  typedef itksys::hash_map< VertexType, ContourRef, VertexHash > VertexToContourMap;
  typedef typename VertexToContourMap::iterator                  VertexMapIterator;
  typedef typename VertexToContourMap::value_type                VertexContourRefPair;

  // The contours we find in the image are stored here
  ContourContainer m_Contours;

  // And indexed by their beginning and ending points here
  VertexToContourMap m_ContourStarts;
  VertexToContourMap m_ContourEnds;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkContourExtractor2DImageFilter.hxx"
#endif

#endif