PCL点云条件滤波

 条件滤波器通过设定滤波条件进行滤波，有点分段函数的味道，当点云在一定范围则留下，不在则舍弃。

#include <iostream>
#include <pcl/point_types.h>
#include <pcl/filters/radius_outlier_removal.h>
#include <pcl/filters/conditional_removal.h>

int main (int argc, char** argv)
{
  if (argc != 2)  //确保输入的参数
  {
    std::cerr << "please specify command line arg '-r' or '-c'" << std::endl;
    exit(0);
  }
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_filtered (new pcl::PointCloud<pcl::PointXYZ>);

  //填充点云
  cloud->width  = 5;
  cloud->height = 1;
  cloud->points.resize (cloud->width * cloud->height);

  for (size_t i = 0; i < cloud->points.size (); ++i)
  {
    cloud->points[i].x = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud->points[i].y = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud->points[i].z = 1024 * rand () / (RAND_MAX + 1.0f);
  }

  if (strcmp(argv[1], "-r") == 0){
    pcl::RadiusOutlierRemoval<pcl::PointXYZ> outrem;  //创建滤波器
    
    outrem.setInputCloud(cloud);    //设置输入点云
    outrem.setRadiusSearch(0.8);     //设置半径为0.8的范围内找临近点
    outrem.setMinNeighborsInRadius (2); //设置查询点的邻域点集数小于2的删除
    // apply filter
    outrem.filter (*cloud_filtered);     //执行条件滤波   在半径为0.8 在此半径内必须要有两个邻居点，此点才会保存
  }
  else if (strcmp(argv[1], "-c") == 0){
    //创建条件限定的下的滤波器
    pcl::ConditionAnd<pcl::PointXYZ>::Ptr range_cond (new
      pcl::ConditionAnd<pcl::PointXYZ> ());   //创建条件定义对象
      //为条件定义对象添加比较算子
    range_cond->addComparison (pcl::FieldComparison<pcl::PointXYZ>::ConstPtr (new
      pcl::FieldComparison<pcl::PointXYZ> ("z", pcl::ComparisonOps::GT, 0.0)));   //添加在Z字段上大于0的比较算子

    range_cond->addComparison (pcl::FieldComparison<pcl::PointXYZ>::ConstPtr (new
      pcl::FieldComparison<pcl::PointXYZ> ("z", pcl::ComparisonOps::LT, 0.8)));   //添加在Z字段上小于0.8的比较算子
    // 创建滤波器并用条件定义对象初始化
    pcl::ConditionalRemoval<pcl::PointXYZ> condrem;
    condrem.setCondition (range_cond);               
    condrem.setInputCloud (cloud);                   //输入点云
    condrem.setKeepOrganized(true);               //设置保持点云的结构
    // 执行滤波
    condrem.filter (*cloud_filtered);  //大于0.0小于0.8这两个条件用于建立滤波器
  }
  else{
    std::cerr << "please specify command line arg '-r' or '-c'" << std::endl;
    exit(0);
  }
  std::cerr << "Cloud before filtering: " << std::endl;
  for (size_t i = 0; i < cloud->points.size (); ++i)
    std::cerr << "    " << cloud->points[i].x << " "
                        << cloud->points[i].y << " "
                        << cloud->points[i].z << std::endl;
  // display pointcloud after filtering
  std::cerr << "Cloud after filtering: " << std::endl;
  for (size_t i = 0; i < cloud_filtered->points.size (); ++i)
    std::cerr << "    " << cloud_filtered->points[i].x << " "
                        << cloud_filtered->points[i].y << " "
                        << cloud_filtered->points[i].z << std::endl;
  return (0);
}