点云库PCL学习——ConditionalRemoval和RadiusOutlierRemoval滤波

一、ConditionalRemoval滤波器
它可以一次删除满足对输入的点云设定的一个或多个条件指标的所有数据点。
下面例子，我们使用“z”轴方向上大于0.0和小于800这两个条件来建立滤波器。

#include <pcl/point_types.h>
#include <pcl/filters/conditional_removal.h>
int main() {
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_filtered(new pcl::PointCloud<pcl::PointXYZ>);
	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);
	}
	//上面的就是创建点云数据
	pcl::ConditionAnd<pcl::PointXYZ>::Ptr range_cond(new pcl::ConditionAnd<pcl::PointXYZ>());   //创建条件定义对象
	range_cond->addComparison(pcl::FieldComparison<pcl::PointXYZ>::ConstPtr(new pcl::FieldComparison<pcl::PointXYZ>("z", pcl::ComparisonOps::GT, 0.0)));
	range_cond->addComparison(pcl::FieldComparison<pcl::PointXYZ>::ConstPtr(new pcl::FieldComparison<pcl::PointXYZ>("z", pcl::ComparisonOps::LT,800)));
	//创建滤波器并用条件定义对象初始化
	pcl::ConditionalRemoval<pcl::PointXYZ> condrem(range_cond);
	condrem.setInputCloud(cloud);
	condrem.setKeepOrganized(true);
	condrem.filter(*cloud_filtered);
	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;

	}
	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;

	}
	system("pause");
	return 0;
}

二、RadiusOutlierRemoval滤波器
去除设置半径内点数少于设定数的点，认定其为离群点。

#include <pcl/filters/radius_outlier_removal.h>
    pcl::RadiusOutlierRemoval<pcl::PointXYZ> outrem; //创建滤波器
	outrem.setInputCloud(cloud);
	outrem.setRadiusSearch(500);     //设置搜索半径
	outrem.setMinNeighborsInRadius(2);//设置最小数
	outrem.filter(*cloud_filtered);

相比之下，RadiusOutlierRemoval滤波器非常适合去除单个的离群点。
而ConditionalRemoval比较灵活，可以根据设置的条件进行过滤，有点像直通滤波。