PCL點雲條件濾波

 條件濾波器通過設定濾波條件進行濾波，有點分段函數的味道，當點雲在一定範圍則留下，不在則捨棄。

#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)  //確保輸入的參數
  {
    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>);

  //填充點雲
  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;  //創建濾波器
    
    outrem.setInputCloud(cloud);    //設置輸入點雲
    outrem.setRadiusSearch(0.8);     //設置半徑爲0.8的範圍內找臨近點
    outrem.setMinNeighborsInRadius (2); //設置查詢點的鄰域點集數小於2的刪除
    // apply filter
    outrem.filter (*cloud_filtered);     //執行條件濾波   在半徑爲0.8 在此半徑內必須要有兩個鄰居點，此點纔會保存
  }
  else if (strcmp(argv[1], "-c") == 0){
    //創建條件限定的下的濾波器
    pcl::ConditionAnd<pcl::PointXYZ>::Ptr range_cond (new
      pcl::ConditionAnd<pcl::PointXYZ> ());   //創建條件定義對象
      //爲條件定義對象添加比較算子
    range_cond->addComparison (pcl::FieldComparison<pcl::PointXYZ>::ConstPtr (new
      pcl::FieldComparison<pcl::PointXYZ> ("z", pcl::ComparisonOps::GT, 0.0)));   //添加在Z字段上大於0的比較算子

    range_cond->addComparison (pcl::FieldComparison<pcl::PointXYZ>::ConstPtr (new
      pcl::FieldComparison<pcl::PointXYZ> ("z", pcl::ComparisonOps::LT, 0.8)));   //添加在Z字段上小於0.8的比較算子
    // 創建濾波器並用條件定義對象初始化
    pcl::ConditionalRemoval<pcl::PointXYZ> condrem;
    condrem.setCondition (range_cond);               
    condrem.setInputCloud (cloud);                   //輸入點雲
    condrem.setKeepOrganized(true);               //設置保持點雲的結構
    // 執行濾波
    condrem.filter (*cloud_filtered);  //大於0.0小於0.8這兩個條件用於建立濾波器
  }
  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);
}