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#ifndef PCL_KEYPOINTS_UNIFORM_SAMPLING_H_
#define PCL_KEYPOINTS_UNIFORM_SAMPLING_H_

#include <pcl/keypoints/keypoint.h>
#include <boost/unordered_map.hpp>

namespace pcl
{
  /** \brief @b UniformSampling assembles a local 3D grid over a given PointCloud, and downsamples + filters the data.
    *
    * The @b UniformSampling class creates a *3D voxel grid* (think about a voxel
    * grid as a set of tiny 3D boxes in space) over the input point cloud data.
    * Then, in each *voxel* (i.e., 3D box), all the points present will be
    * approximated (i.e., *downsampled*) with their centroid. This approach is
    * a bit slower than approximating them with the center of the voxel, but it
    * represents the underlying surface more accurately.
    *
    * \author Radu Bogdan Rusu
    * \ingroup keypoints
    */
  template <typename PointInT>
  class UniformSampling: public Keypoint<PointInT, int>
  {
    typedef typename Keypoint<PointInT, int>::PointCloudIn PointCloudIn;
    typedef typename Keypoint<PointInT, int>::PointCloudOut PointCloudOut;

    using Keypoint<PointInT, int>::name_;
    using Keypoint<PointInT, int>::input_;
    using Keypoint<PointInT, int>::indices_;
    using Keypoint<PointInT, int>::search_radius_;
    using Keypoint<PointInT, int>::getClassName;

    public:
      typedef boost::shared_ptr<UniformSampling<PointInT> > Ptr;
      typedef boost::shared_ptr<const UniformSampling<PointInT> > ConstPtr;

      /** \brief Empty constructor. */
      UniformSampling () :
        leaves_ (),
        leaf_size_ (Eigen::Vector4f::Zero ()),
        inverse_leaf_size_ (Eigen::Vector4f::Zero ()),
        min_b_ (Eigen::Vector4i::Zero ()),
        max_b_ (Eigen::Vector4i::Zero ()),
        div_b_ (Eigen::Vector4i::Zero ()),
        divb_mul_ (Eigen::Vector4i::Zero ())
      {
        name_ = "UniformSampling";
      }

      /** \brief Destructor. */
      virtual ~UniformSampling ()
      {
        leaves_.clear();
      }

      /** \brief Set the 3D grid leaf size.
        * \param radius the 3D grid leaf size
        */
      virtual inline void 
      setRadiusSearch (double radius) 
      { 
        leaf_size_[0] = leaf_size_[1] = leaf_size_[2] = static_cast<float> (radius);
        // Avoid division errors
        if (leaf_size_[3] == 0)
          leaf_size_[3] = 1;
        // Use multiplications instead of divisions
        inverse_leaf_size_ = Eigen::Array4f::Ones () / leaf_size_.array ();
        search_radius_ = radius;
      }

    protected:
      /** \brief Simple structure to hold an nD centroid and the number of points in a leaf. */
      struct Leaf
      {
        Leaf () : idx (-1) { }
        int idx;
      };

      /** \brief The 3D grid leaves. */
      boost::unordered_map<size_t, Leaf> leaves_;

      /** \brief The size of a leaf. */
      Eigen::Vector4f leaf_size_;

      /** \brief Internal leaf sizes stored as 1/leaf_size_ for efficiency reasons. */ 
      Eigen::Array4f inverse_leaf_size_;

      /** \brief The minimum and maximum bin coordinates, the number of divisions, and the division multiplier. */
      Eigen::Vector4i min_b_, max_b_, div_b_, divb_mul_;

      /** \brief Downsample a Point Cloud using a voxelized grid approach
        * \param output the resultant point cloud message
        */
      void 
      detectKeypoints (PointCloudOut &output);
  };
}

#ifdef PCL_NO_PRECOMPILE
#include <pcl/keypoints/impl/uniform_sampling.hpp>
#endif

#endif  //#ifndef PCL_KEYPOINTS_UNIFORM_SAMPLING_H_

