3d激光雷达开发（欧几里得聚类算法）

Posted 2022-03-17 费晓行

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         图形处理里面有一个聚类算法，叫k-means。基本思想就是默认图像里面有k个区域，每个区域都可以内部聚合、外部松散的组合体，找到了这k个区域，就可以实现图像的分割了。正好，点云算法里面也有类似的一个算法，称之为欧几里得聚类算法，https://pcl.readthedocs.io/projects/tutorials/en/master/cluster_extraction.html#cluster-extraction

1、代码内容

#include <pcl/ModelCoefficients.h>
#include <pcl/point_types.h>
#include <pcl/io/pcd_io.h>
#include <pcl/filters/extract_indices.h>
#include <pcl/filters/voxel_grid.h>
#include <pcl/features/normal_3d.h>
#include <pcl/search/kdtree.h>
#include <pcl/sample_consensus/method_types.h>
#include <pcl/sample_consensus/model_types.h>
#include <pcl/segmentation/sac_segmentation.h>
#include <pcl/segmentation/extract_clusters.h>


int 
main ()

  // Read in the cloud data
  pcl::PCDReader reader;
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>), cloud_f (new pcl::PointCloud<pcl::PointXYZ>);
  reader.read ("table_scene_lms400.pcd", *cloud);
  std::cout << "PointCloud before filtering has: " << cloud->size () << " data points." << std::endl; //*

  // Create the filtering object: downsample the dataset using a leaf size of 1cm
  pcl::VoxelGrid<pcl::PointXYZ> vg;
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_filtered (new pcl::PointCloud<pcl::PointXYZ>);
  vg.setInputCloud (cloud);
  vg.setLeafSize (0.01f, 0.01f, 0.01f);
  vg.filter (*cloud_filtered);
  std::cout << "PointCloud after filtering has: " << cloud_filtered->size ()  << " data points." << std::endl; //*

  // Create the segmentation object for the planar model and set all the parameters
  pcl::SACSegmentation<pcl::PointXYZ> seg;
  pcl::PointIndices::Ptr inliers (new pcl::PointIndices);
  pcl::ModelCoefficients::Ptr coefficients (new pcl::ModelCoefficients);
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_plane (new pcl::PointCloud<pcl::PointXYZ> ());
  pcl::PCDWriter writer;
  seg.setOptimizeCoefficients (true);
  seg.setModelType (pcl::SACMODEL_PLANE);
  seg.setMethodType (pcl::SAC_RANSAC);
  seg.setMaxIterations (100);
  seg.setDistanceThreshold (0.02);

  int nr_points = (int) cloud_filtered->size ();
  while (cloud_filtered->size () > 0.3 * nr_points)
  
    // Segment the largest planar component from the remaining cloud
    seg.setInputCloud (cloud_filtered);
    seg.segment (*inliers, *coefficients);
    if (inliers->indices.size () == 0)
    
      std::cout << "Could not estimate a planar model for the given dataset." << std::endl;
      break;
    

    // Extract the planar inliers from the input cloud
    pcl::ExtractIndices<pcl::PointXYZ> extract;
    extract.setInputCloud (cloud_filtered);
    extract.setIndices (inliers);
    extract.setNegative (false);

    // Get the points associated with the planar surface
    extract.filter (*cloud_plane);
    std::cout << "PointCloud representing the planar component: " << cloud_plane->size () << " data points." << std::endl;

    // Remove the planar inliers, extract the rest
    extract.setNegative (true);
    extract.filter (*cloud_f);
    *cloud_filtered = *cloud_f;
  

  // Creating the KdTree object for the search method of the extraction
  pcl::search::KdTree<pcl::PointXYZ>::Ptr tree (new pcl::search::KdTree<pcl::PointXYZ>);
  tree->setInputCloud (cloud_filtered);

  std::vector<pcl::PointIndices> cluster_indices;
  pcl::EuclideanClusterExtraction<pcl::PointXYZ> ec;
  ec.setClusterTolerance (0.02); // 2cm
  ec.setMinClusterSize (100);
  ec.setMaxClusterSize (25000);
  ec.setSearchMethod (tree);
  ec.setInputCloud (cloud_filtered);
  ec.extract (cluster_indices);

  int j = 0;
  for (std::vector<pcl::PointIndices>::const_iterator it = cluster_indices.begin (); it != cluster_indices.end (); ++it)
  
    pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_cluster (new pcl::PointCloud<pcl::PointXYZ>);
    for (const auto& idx : it->indices)
      cloud_cluster->push_back ((*cloud_filtered)[idx]); //*
    cloud_cluster->width = cloud_cluster->size ();
    cloud_cluster->height = 1;
    cloud_cluster->is_dense = true;

    std::cout << "PointCloud representing the Cluster: " << cloud_cluster->size () << " data points." << std::endl;
    std::stringstream ss;
    ss << "cloud_cluster_" << j << ".pcd";
    writer.write<pcl::PointXYZ> (ss.str (), *cloud_cluster, false); //*
    j++;
  

  return (0);

2、代码分析

        整个代码的内容比较简单，主要就是先除去平面，再进行分割。

3、准备CMakeLists.txt

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

project(cluster)

find_package(PCL 1.2 REQUIRED)

include_directories($PCL_INCLUDE_DIRS)
link_directories($PCL_LIBRARY_DIRS)
add_definitions($PCL_DEFINITIONS)

add_executable (cluster cluster.cpp)
target_link_libraries (cluster $PCL_LIBRARIES)

4、准备sln，开始编译

5、运行 exe

        不出意外，应该可以看到这几个文件，