一、概述

  提取多边形内部的点。

二、代码

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/filters/crop_hull.h>
#include <pcl/surface/concave_hull.h>
#include <pcl/surface/convex_hull.h>
#include <pcl/visualization/cloud_viewer.h>

int main(int argc, char** argv)
{
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);//加载点云数据
	pcl::PCDReader reader;
	reader.read("pig2.pcd", *cloud);

	pcl::PointCloud<pcl::PointXYZ>::Ptr bound(new pcl::PointCloud<pcl::PointXYZ>); //创建多边形区域指针
	bound->push_back(pcl::PointXYZ(0.1, 0.1, 0));								   //根据顶点坐标创建区域
	bound->push_back(pcl::PointXYZ(0.1, -0.1, 0));
	bound->push_back(pcl::PointXYZ(-0.1, 0.1, 0));
	bound->push_back(pcl::PointXYZ(-0.1, -0.1, 0));
	bound->push_back(pcl::PointXYZ(0.15, 0.1, 0));

	pcl::ConvexHull<pcl::PointXYZ> hull; //建立一个凸包对象
	hull.setInputCloud(bound);           //输入设置好的凸包范围
	hull.setDimension(2);				 //设置凸包的维度
	std::vector<pcl::Vertices> polygons; //设置动态数组用于保存凸包顶点
	//设置点云用于描述凸包的形状
	pcl::PointCloud<pcl::PointXYZ>::Ptr surface_hull(new pcl::PointCloud<pcl::PointXYZ>); 
	hull.reconstruct(*surface_hull, polygons);	//计算凸包结果

	pcl::PointCloud<pcl::PointXYZ>::Ptr objects(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::CropHull<pcl::PointXYZ> crop;	//创建CropHull对象
	crop.setDim(2);					    //设置维度
	crop.setInputCloud(cloud);			//设置输入点云
	crop.setHullIndices(polygons);		//输入封闭多边形的顶点
	crop.setHullCloud(surface_hull);	//输入封闭多边形的形状
	crop.filter(*objects);				//执行CropHull滤波并存储相应的结果
	std::cout << "Cloud after crop has:" << objects->size() << " data points." << std::endl;
	//初始化共享指针用于进行可视化
	boost::shared_ptr<pcl::visualization::PCLVisualizer> view(new pcl::visualization::PCLVisualizer("crophull display"));
	view->setBackgroundColor(255, 255, 255);
	
	//利用多视口输出可视化结果
	int v1(0);
	view->createViewPort(0.0, 0.0, 0.33, 1, v1);
	view->setBackgroundColor(255, 255, 255, v1);
	view->addPointCloud(cloud, "cloud", v1);
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR, 1, 0, 0, "cloud");
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "cloud");
	view->addPolygon<pcl::PointXYZ>(surface_hull, 0, .069 * 255, 0.2 * 255, "backview_hull_polyLine1", v1);

	int v2(0);
	view->createViewPort(0.33, 0.0, 0.66, 1, v2);
	view->setBackgroundColor(255, 255, 255, v2);
	view->addPointCloud(surface_hull, "surface_hull", v2);
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR, 1, 0, 1, "surface_hull");
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 8, "surface_hull");
	view->addPolygon<pcl::PointXYZ>(surface_hull, 0, .069 * 255, 0.2 * 255, "backview_hull_polyLine1", v2);

	int v3(0);
	view->createViewPort(0.66, 0.0, 1, 1, v3);
	view->setBackgroundColor(255, 255, 255, v3);
	view->addPointCloud(objects, "objects", v3);
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR, 0, 1, 0, "objects");
	view->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "objects");

	while (!view->wasStopped())
	{
		view->spinOnce(1000);
	}

	system("pause");
	return 0;
}

二、结果