grid_minimum.h

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#ifndef PCL_FILTERS_VOXEL_GRID_MINIMUM_H_
#define PCL_FILTERS_VOXEL_GRID_MINIMUM_H_

#include <pcl/filters/boost.h>
#include <pcl/filters/filter.h>
#include <pcl/filters/filter_indices.h>

namespace pcl
{
  /** \brief GridMinimum assembles a local 2D grid over a given PointCloud, and downsamples the data.
    *
    * The GridMinimum class creates a *2D grid* over the input point cloud
    * data. Then, in each *cell* (i.e., 2D grid element), all the points
    * present will be *downsampled* with the minimum z value. This grid minimum
    * can be useful in a number of topographic processing tasks such as crudely
    * estimating ground returns, especially under foliage.
    *
    * \author Bradley J Chambers
    * \ingroup filters
    */
  template <typename PointT>
  class GridMinimum: public FilterIndices<PointT>
  {
    protected:
      using Filter<PointT>::filter_name_;
      using Filter<PointT>::getClassName;
      using Filter<PointT>::input_;
      using Filter<PointT>::indices_;

      typedef typename FilterIndices<PointT>::PointCloud PointCloud;

    public:
      /** \brief Empty constructor. */
      GridMinimum (const float resolution)
      {
        setResolution (resolution);
        filter_name_ = "GridMinimum";
      }

      /** \brief Destructor. */
      virtual ~GridMinimum ()
      {
      }

      /** \brief Set the grid resolution.
        * \param[in] resolution the grid resolution
        */
      inline void
      setResolution (const float resolution)
      {
        resolution_ = resolution;
        // Use multiplications instead of divisions
        inverse_resolution_ = 1.0f / resolution_;
      }

      /** \brief Get the grid resolution. */
      inline float
      getResolution () { return (resolution_); }

    protected:
      /** \brief The resolution. */
      float resolution_;

      /** \brief Internal resolution stored as 1/resolution_ for efficiency reasons. */
      float inverse_resolution_;

      /** \brief Downsample a Point Cloud using a 2D grid approach
        * \param[out] output the resultant point cloud message
        */
      void
      applyFilter (PointCloud &output);

      /** \brief Filtered results are indexed by an indices array.
        * \param[out] indices The resultant indices.
        */
      void
      applyFilter (std::vector<int> &indices)
      {
        applyFilterIndices (indices);
      }

      /** \brief Filtered results are indexed by an indices array.
        * \param[out] indices The resultant indices.
        */
      void
      applyFilterIndices (std::vector<int> &indices);

  };
}

#ifdef PCL_NO_PRECOMPILE
#include <pcl/filters/impl/grid_minimum.hpp>
#endif

#endif  //#ifndef PCL_FILTERS_VOXEL_GRID_MINIMUM_H_