statistical_outlier_removal.h

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#ifndef PCL_FILTERS_STATISTICAL_OUTLIER_REMOVAL_H_
#define PCL_FILTERS_STATISTICAL_OUTLIER_REMOVAL_H_

#include <pcl/filters/filter_indices.h>
#include <pcl/search/pcl_search.h>

namespace pcl
{
  /** \brief @b StatisticalOutlierRemoval uses point neighborhood statistics to filter outlier data.
    * \details The algorithm iterates through the entire input twice:
    * During the first iteration it will compute the average distance that each point has to its nearest k neighbors.
    * The value of k can be set using setMeanK().
    * Next, the mean and standard deviation of all these distances are computed in order to determine a distance threshold.
    * The distance threshold will be equal to: mean + stddev_mult * stddev.
    * The multiplier for the standard deviation can be set using setStddevMulThresh().
    * During the next iteration the points will be classified as inlier or outlier if their average neighbor distance is below or above this threshold respectively.
    * <br>
    * The neighbors found for each query point will be found amongst ALL points of setInputCloud(), not just those indexed by setIndices().
    * The setIndices() method only indexes the points that will be iterated through as search query points.
    * <br><br>
    * For more information:
    *   - R. B. Rusu, Z. C. Marton, N. Blodow, M. Dolha, and M. Beetz.
    *     Towards 3D Point Cloud Based Object Maps for Household Environments
    *     Robotics and Autonomous Systems Journal (Special Issue on Semantic Knowledge), 2008.
    * <br><br>
    * Usage example:
    * \code
    * pcl::StatisticalOutlierRemoval<PointType> sorfilter (true); // Initializing with true will allow us to extract the removed indices
    * sorfilter.setInputCloud (cloud_in);
    * sorfilter.setMeanK (8);
    * sorfilter.setStddevMulThresh (1.0);
    * sorfilter.filter (*cloud_out);
    * // The resulting cloud_out contains all points of cloud_in that have an average distance to their 8 nearest neighbors that is below the computed threshold
    * // Using a standard deviation multiplier of 1.0 and assuming the average distances are normally distributed there is a 84.1% chance that a point will be an inlier
    * indices_rem = sorfilter.getRemovedIndices ();
    * // The indices_rem array indexes all points of cloud_in that are outliers
    * \endcode
    * \author Radu Bogdan Rusu
    * \ingroup filters
    */
  template<typename PointT>
  class StatisticalOutlierRemoval : public FilterIndices<PointT>
  {
    protected:
      typedef typename FilterIndices<PointT>::PointCloud PointCloud;
      typedef typename PointCloud::Ptr PointCloudPtr;
      typedef typename PointCloud::ConstPtr PointCloudConstPtr;
      typedef typename pcl::search::Search<PointT>::Ptr SearcherPtr;

    public:

      typedef boost::shared_ptr< StatisticalOutlierRemoval<PointT> > Ptr;
      typedef boost::shared_ptr< const StatisticalOutlierRemoval<PointT> > ConstPtr;


      /** \brief Constructor.
        * \param[in] extract_removed_indices Set to true if you want to be able to extract the indices of points being removed (default = false).
        */
      StatisticalOutlierRemoval (bool extract_removed_indices = false) :
        FilterIndices<PointT>::FilterIndices (extract_removed_indices),
        searcher_ (),
        mean_k_ (1),
        std_mul_ (0.0)
      {
        filter_name_ = "StatisticalOutlierRemoval";
      }

      /** \brief Set the number of nearest neighbors to use for mean distance estimation.
        * \param[in] nr_k The number of points to use for mean distance estimation.
        */
      inline void
      setMeanK (int nr_k)
      {
        mean_k_ = nr_k;
      }

      /** \brief Get the number of nearest neighbors to use for mean distance estimation.
        * \return The number of points to use for mean distance estimation.
        */
      inline int
      getMeanK ()
      {
        return (mean_k_);
      }

      /** \brief Set the standard deviation multiplier for the distance threshold calculation.
        * \details The distance threshold will be equal to: mean + stddev_mult * stddev.
        * Points will be classified as inlier or outlier if their average neighbor distance is below or above this threshold respectively.
        * \param[in] stddev_mult The standard deviation multiplier.
        */
      inline void
      setStddevMulThresh (double stddev_mult)
      {
        std_mul_ = stddev_mult;
      }

      /** \brief Get the standard deviation multiplier for the distance threshold calculation.
        * \details The distance threshold will be equal to: mean + stddev_mult * stddev.
        * Points will be classified as inlier or outlier if their average neighbor distance is below or above this threshold respectively.
        */
      inline double
      getStddevMulThresh ()
      {
        return (std_mul_);
      }

    protected:
      using PCLBase<PointT>::input_;
      using PCLBase<PointT>::indices_;
      using Filter<PointT>::filter_name_;
      using Filter<PointT>::getClassName;
      using FilterIndices<PointT>::negative_;
      using FilterIndices<PointT>::keep_organized_;
      using FilterIndices<PointT>::user_filter_value_;
      using FilterIndices<PointT>::extract_removed_indices_;
      using FilterIndices<PointT>::removed_indices_;

      /** \brief Filtered results are stored in a separate point cloud.
        * \param[out] output The resultant point cloud.
        */
      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);

    private:
      /** \brief A pointer to the spatial search object. */
      SearcherPtr searcher_;

      /** \brief The number of points to use for mean distance estimation. */
      int mean_k_;

      /** \brief Standard deviations threshold (i.e., points outside of 
        * \f$ \mu \pm \sigma \cdot std\_mul \f$ will be marked as outliers). */
      double std_mul_;
  };

  /** \brief @b StatisticalOutlierRemoval uses point neighborhood statistics to filter outlier data. For more
    * information check:
    *   - R. B. Rusu, Z. C. Marton, N. Blodow, M. Dolha, and M. Beetz.
    *     Towards 3D Point Cloud Based Object Maps for Household Environments
    *     Robotics and Autonomous Systems Journal (Special Issue on Semantic Knowledge), 2008.
    *
    * \note setFilterFieldName (), setFilterLimits (), and setFilterLimitNegative () are ignored.
    * \author Radu Bogdan Rusu
    * \ingroup filters
    */
  template<>
  class PCL_EXPORTS StatisticalOutlierRemoval<pcl::PCLPointCloud2> : public Filter<pcl::PCLPointCloud2>
  {
    using Filter<pcl::PCLPointCloud2>::filter_name_;
    using Filter<pcl::PCLPointCloud2>::getClassName;

    using Filter<pcl::PCLPointCloud2>::removed_indices_;
    using Filter<pcl::PCLPointCloud2>::extract_removed_indices_;

    typedef pcl::search::Search<pcl::PointXYZ> KdTree;
    typedef pcl::search::Search<pcl::PointXYZ>::Ptr KdTreePtr;

    typedef pcl::PCLPointCloud2 PCLPointCloud2;
    typedef PCLPointCloud2::Ptr PCLPointCloud2Ptr;
    typedef PCLPointCloud2::ConstPtr PCLPointCloud2ConstPtr;

    public:
      /** \brief Empty constructor. */
      StatisticalOutlierRemoval (bool extract_removed_indices = false) :
        Filter<pcl::PCLPointCloud2>::Filter (extract_removed_indices), mean_k_ (2),
        std_mul_ (0.0), tree_ (), negative_ (false)
      {
        filter_name_ = "StatisticalOutlierRemoval";
      }

      /** \brief Set the number of points (k) to use for mean distance estimation
        * \param nr_k the number of points to use for mean distance estimation
        */
      inline void
      setMeanK (int nr_k)
      {
        mean_k_ = nr_k;
      }

      /** \brief Get the number of points to use for mean distance estimation. */
      inline int
      getMeanK ()
      {
        return (mean_k_);
      }

      /** \brief Set the standard deviation multiplier threshold. All points outside the
        * \f[ \mu \pm \sigma \cdot std\_mul \f]
        * will be considered outliers, where \f$ \mu \f$ is the estimated mean,
        * and \f$ \sigma \f$ is the standard deviation.
        * \param std_mul the standard deviation multiplier threshold
        */
      inline void
      setStddevMulThresh (double std_mul)
      {
        std_mul_ = std_mul;
      }

      /** \brief Get the standard deviation multiplier threshold as set by the user. */
      inline double
      getStddevMulThresh ()
      {
        return (std_mul_);
      }

      /** \brief Set whether the indices should be returned, or all points \e except the indices.
        * \param negative true if all points \e except the input indices will be returned, false otherwise
        */
      inline void
      setNegative (bool negative)
      {
        negative_ = negative;
      }

      /** \brief Get the value of the internal #negative_ parameter. If
        * true, all points \e except the input indices will be returned.
        * \return The value of the "negative" flag
        */
      inline bool
      getNegative ()
      {
        return (negative_);
      }

    protected:
      /** \brief The number of points to use for mean distance estimation. */
      int mean_k_;

      /** \brief Standard deviations threshold (i.e., points outside of 
        * \f$ \mu \pm \sigma \cdot std\_mul \f$ will be marked as outliers). 
        */
      double std_mul_;

      /** \brief A pointer to the spatial search object. */
      KdTreePtr tree_;

      /** \brief If true, the outliers will be returned instead of the inliers (default: false). */
      bool negative_;

      void
      applyFilter (PCLPointCloud2 &output);
  };
}

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

#endif  // PCL_FILTERS_STATISTICAL_OUTLIER_REMOVAL_H_