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#ifndef PCL_COMMON_CORRESPONDENCE_H_
#define PCL_COMMON_CORRESPONDENCE_H_

#ifdef __GNUC__
#pragma GCC system_header 
#endif

#include <boost/shared_ptr.hpp>
#include <Eigen/StdVector>
#include <Eigen/Geometry>
#include <pcl/pcl_exports.h>

namespace pcl
{
  /** \brief Correspondence represents a match between two entities (e.g., points, descriptors, etc). This is 
    * represesented via the indices of a \a source point and a \a target point, and the distance between them.
    *
    * \author Dirk Holz, Radu B. Rusu, Bastian Steder
    * \ingroup common
    */
  struct Correspondence
  {
    /** \brief Index of the query (source) point. */
    int index_query;
    /** \brief Index of the matching (target) point. Set to -1 if no correspondence found. */
    int index_match;
    /** \brief Distance between the corresponding points, or the weight denoting the confidence in correspondence estimation */
    union
    {
      float distance;
      float weight;
    };
    
    /** \brief Standard constructor. 
      * Sets \ref index_query to 0, \ref index_match to -1, and \ref distance to FLT_MAX.
      */
    inline Correspondence () : index_query (0), index_match (-1), 
                               distance (std::numeric_limits<float>::max ())
    {}

    /** \brief Constructor. */
    inline Correspondence (int _index_query, int _index_match, float _distance) : 
      index_query (_index_query), index_match (_index_match), distance (_distance)
    {}

    /** \brief Empty destructor. */
    virtual ~Correspondence () {}
    
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
  };
  
  /** \brief overloaded << operator */
  PCL_EXPORTS std::ostream& operator << (std::ostream& os, const Correspondence& c);

  typedef std::vector< pcl::Correspondence, Eigen::aligned_allocator<pcl::Correspondence> > Correspondences;
  typedef boost::shared_ptr<Correspondences> CorrespondencesPtr;
  typedef boost::shared_ptr<const Correspondences > CorrespondencesConstPtr;

  /**
    * \brief Get the query points of correspondences that are present in
    * one correspondence vector but not in the other, e.g., to compare
    * correspondences before and after rejection.
    * \param[in] correspondences_before Vector of correspondences before rejection
    * \param[in] correspondences_after Vector of correspondences after rejection
    * \param[out] indices Query point indices of correspondences that have been rejected
    * \param[in] presorting_required Enable/disable internal sorting of vectors.
    * By default (true), vectors are internally sorted before determining their difference.
    * If the order of correspondences in \a correspondences_after is not different (has not been changed)
    * from the order in \b correspondences_before this pre-processing step can be disabled
    * in order to gain efficiency. In order to disable pre-sorting set \a presorting_requered to false.
    */
  void
  getRejectedQueryIndices (const pcl::Correspondences &correspondences_before,
                           const pcl::Correspondences &correspondences_after,
                           std::vector<int>& indices,
                           bool presorting_required = true);

  /**
    * \brief Representation of a (possible) correspondence between two 3D points in two different coordinate frames
    *        (e.g. from feature matching)
    * \ingroup common
    */
  struct PointCorrespondence3D : public Correspondence
  {
    Eigen::Vector3f point1;  //!< The 3D position of the point in the first coordinate frame
    Eigen::Vector3f point2;  //!< The 3D position of the point in the second coordinate frame

    /** \brief Empty constructor. */
    PointCorrespondence3D () : point1 (), point2 () {}

    /** \brief Empty destructor. */
    virtual ~PointCorrespondence3D () {}
    
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
  };
  typedef std::vector<PointCorrespondence3D, Eigen::aligned_allocator<PointCorrespondence3D> > PointCorrespondences3DVector;

  /**
    * \brief Representation of a (possible) correspondence between two points (e.g. from feature matching),
    *        that encode complete 6DOF transoformations.
    * \ingroup common
    */
  struct PointCorrespondence6D : public PointCorrespondence3D
  {
    Eigen::Affine3f transformation;  //!< The transformation to go from the coordinate system
                                        //!< of point2 to the coordinate system of point1
    /** \brief Empty destructor. */
    virtual ~PointCorrespondence6D () {}

    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
  };
  typedef std::vector<PointCorrespondence6D, Eigen::aligned_allocator<PointCorrespondence6D> > PointCorrespondences6DVector;

  /**
    * \brief Comparator to enable us to sort a vector of PointCorrespondences according to their scores using
    *        std::sort (begin(), end(), isBetterCorrespondence);
    * \ingroup common
    */
  inline bool
  isBetterCorrespondence (const Correspondence &pc1, const Correspondence &pc2)
  {
    return (pc1.distance > pc2.distance);
  }
}

#endif /* PCL_COMMON_CORRESPONDENCE_H_ */
