approximate_progressive_morphological_filter.hpp

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#ifndef PCL_SEGMENTATION_APPROXIMATE_PROGRESSIVE_MORPHOLOGICAL_FILTER_HPP_
#define PCL_SEGMENTATION_APPROXIMATE_PROGRESSIVE_MORPHOLOGICAL_FILTER_HPP_
 
#include <pcl/common/common.h>
#include <pcl/common/io.h>
#include <pcl/filters/morphological_filter.h>
#include <pcl/filters/extract_indices.h>
#include <pcl/segmentation/approximate_progressive_morphological_filter.h>
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>
 
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template <typename PointT>
pcl::ApproximateProgressiveMorphologicalFilter<PointT>::ApproximateProgressiveMorphologicalFilter () :
  max_window_size_ (33),
  slope_ (0.7f),
  max_distance_ (10.0f),
  initial_distance_ (0.15f),
  cell_size_ (1.0f),
  base_ (2.0f),
  exponential_ (true),
  threads_ (0)
{
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template <typename PointT>
pcl::ApproximateProgressiveMorphologicalFilter<PointT>::~ApproximateProgressiveMorphologicalFilter () = default;
 
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template <typename PointT> void
pcl::ApproximateProgressiveMorphologicalFilter<PointT>::extract (Indices& ground)
{
  bool segmentation_is_possible = initCompute ();
  if (!segmentation_is_possible)
  {
    deinitCompute ();
    return;
  }
 
  // Compute the series of window sizes and height thresholds
  std::vector<float> height_thresholds;
  std::vector<float> window_sizes;
  std::vector<int> half_sizes;
  int iteration = 0;
  float window_size = 0.0f; 
 
  while (window_size < max_window_size_)
  {
    // Determine the initial window size.
    int half_size = (exponential_) ? (static_cast<int> (std::pow (static_cast<float> (base_), iteration))) : ((iteration+1) * base_);
 
    window_size = 2 * half_size + 1;
 
    // Calculate the height threshold to be used in the next iteration.
    float height_threshold = (iteration == 0) ? (initial_distance_) : (slope_ * (window_size - window_sizes[iteration-1]) * cell_size_ + initial_distance_);
 
    // Enforce max distance on height threshold
    if (height_threshold > max_distance_)
      height_threshold = max_distance_;
 
    half_sizes.push_back (half_size);
    window_sizes.push_back (window_size);
    height_thresholds.push_back (height_threshold);
 
    iteration++;
  }
 
  // setup grid based on scale and extents
  Eigen::Vector4f global_max, global_min;
  pcl::getMinMax3D<PointT> (*input_, global_min, global_max);
 
  float xextent = global_max.x () - global_min.x ();
  float yextent = global_max.y () - global_min.y ();
 
  int rows = static_cast<int> (std::floor (yextent / cell_size_) + 1);
  int cols = static_cast<int> (std::floor (xextent / cell_size_) + 1);
 
  Eigen::MatrixXf A (rows, cols);
  A.setConstant (std::numeric_limits<float>::quiet_NaN ());
 
  Eigen::MatrixXf Z (rows, cols);
  Z.setConstant (std::numeric_limits<float>::quiet_NaN ());
 
  Eigen::MatrixXf Zf (rows, cols);
  Zf.setConstant (std::numeric_limits<float>::quiet_NaN ());
 
#pragma omp parallel for \
  default(none) \
  shared(A, global_min) \
  num_threads(threads_)
  for (int i = 0; i < (int)input_->size (); ++i)
  {
    // ...then test for lower points within the cell
    PointT p = (*input_)[i];
    int row = std::floor((p.y - global_min.y ()) / cell_size_);
    int col = std::floor((p.x - global_min.x ()) / cell_size_);
 
    if (p.z < A (row, col) || std::isnan (A (row, col)))
    {
      A (row, col) = p.z;
    }
  }
 
  // Ground indices are initially limited to those points in the input cloud we
  // wish to process
  ground = *indices_;
 
  // Progressively filter ground returns using morphological open
  for (std::size_t i = 0; i < window_sizes.size (); ++i)
  {
    PCL_DEBUG ("      Iteration %d (height threshold = %f, window size = %f, half size = %d)...",
               i, height_thresholds[i], window_sizes[i], half_sizes[i]);
 
    // Limit filtering to those points currently considered ground returns
    typename pcl::PointCloud<PointT>::Ptr cloud (new pcl::PointCloud<PointT>);
    pcl::copyPointCloud<PointT> (*input_, ground, *cloud);
 
    // Apply the morphological opening operation at the current window size.
#pragma omp parallel for \
  default(none) \
  shared(A, cols, half_sizes, i, rows, Z) \
  num_threads(threads_)
    for (int row = 0; row < rows; ++row)
    {
      int rs, re;
      rs = ((row - half_sizes[i]) < 0) ? 0 : row - half_sizes[i];
      re = ((row + half_sizes[i]) > (rows-1)) ? (rows-1) : row + half_sizes[i];
 
      for (int col = 0; col < cols; ++col)
      {
        int cs, ce;
        cs = ((col - half_sizes[i]) < 0) ? 0 : col - half_sizes[i];
        ce = ((col + half_sizes[i]) > (cols-1)) ? (cols-1) : col + half_sizes[i];
 
        float min_coeff = std::numeric_limits<float>::max ();
 
        for (int j = rs; j < (re + 1); ++j)
        {
          for (int k = cs; k < (ce + 1); ++k)
          {
            if (A (j, k) != std::numeric_limits<float>::quiet_NaN ())
            {
              if (A (j, k) < min_coeff)
                min_coeff = A (j, k);
            }
          }
        }
 
        if (min_coeff != std::numeric_limits<float>::max ())
          Z(row, col) = min_coeff;
      }
    }
 
#pragma omp parallel for \
  default(none) \
  shared(cols, half_sizes, i, rows, Z, Zf) \
  num_threads(threads_)
    for (int row = 0; row < rows; ++row)
    {
      int rs, re;
      rs = ((row - half_sizes[i]) < 0) ? 0 : row - half_sizes[i];
      re = ((row + half_sizes[i]) > (rows-1)) ? (rows-1) : row + half_sizes[i];
 
      for (int col = 0; col < cols; ++col)
      {
        int cs, ce;
        cs = ((col - half_sizes[i]) < 0) ? 0 : col - half_sizes[i];
        ce = ((col + half_sizes[i]) > (cols-1)) ? (cols-1) : col + half_sizes[i];
 
        float max_coeff = -std::numeric_limits<float>::max ();
 
        for (int j = rs; j < (re + 1); ++j)
        {
          for (int k = cs; k < (ce + 1); ++k)
          {
            if (Z (j, k) != std::numeric_limits<float>::quiet_NaN ())
            {
              if (Z (j, k) > max_coeff)
                max_coeff = Z (j, k);
            }
          }
        }
 
        if (max_coeff != -std::numeric_limits<float>::max ())
          Zf (row, col) = max_coeff;
      }
    }
 
    // Find indices of the points whose difference between the source and
    // filtered point clouds is less than the current height threshold.
    Indices pt_indices;
    for (std::size_t p_idx = 0; p_idx < ground.size (); ++p_idx)
    {
      PointT p = (*cloud)[p_idx];
      int erow = static_cast<int> (std::floor ((p.y - global_min.y ()) / cell_size_));
      int ecol = static_cast<int> (std::floor ((p.x - global_min.x ()) / cell_size_));
 
      float diff = p.z - Zf (erow, ecol);
      if (diff < height_thresholds[i])
        pt_indices.push_back (ground[p_idx]);
    }
 
    A.swap (Zf);
 
    // Ground is now limited to pt_indices
    ground.swap (pt_indices);
 
    PCL_DEBUG ("ground now has %d points\n", ground.size ());
  }
 
  deinitCompute ();
}
 
 
#define PCL_INSTANTIATE_ApproximateProgressiveMorphologicalFilter(T) template class pcl::ApproximateProgressiveMorphologicalFilter<T>;
 
#endif    // PCL_SEGMENTATION_APPROXIMATE_PROGRESSIVE_MORPHOLOGICAL_FILTER_HPP_