一、算法原理
见《点云库PCL从入门到精通》P164页
二、代码实现
#include <iostream>
#include <vector>
#include <pcl/io/io.h>
#include <pcl/io/pcd_io.h>
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>
#include <pcl/filters/crop_hull.h>
#include <pcl/surface/concave_hull.h>
#include <pcl/visualization/cloud_viewer.h>
using namespace std;
int main(int argc, char** argv)
{
pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);
pcl::PCDReader reader;
reader.read("pig.pcd",*cloud);
//---------为了构造2D封闭多边形，首先输入2D平面点云，这些平面点是2D封闭多边形的顶点。
pcl::PointCloud<pcl::PointXYZ>::Ptr boundingbox_ptr (new pcl::PointCloud<pcl::PointXYZ>);
//boundingbox_ptr->push_back(pcl::PointXYZ(0.1, 0.1, 0));//四个顶点即可
boundingbox_ptr->push_back(pcl::PointXYZ(0.1, -0.1,0 ));
boundingbox_ptr->push_back(pcl::PointXYZ(-0.1, 0.1,0 ));
boundingbox_ptr->push_back(pcl::PointXYZ(-0.1, -0.1,0 ));
boundingbox_ptr->push_back(pcl::PointXYZ(0.15, 0.1,0 ));
//---------对上述2D平面点构造凸包-----------------------
pcl::ConvexHull<pcl::PointXYZ> hull;//创建凸包对象
hull.setInputCloud(boundingbox_ptr);//设置输入点云
hull.setDimension(2);//设置凸包维度
vector<pcl::Vertices> polygons;//设置pcl:Vertices类型的向量，用于保存凸包顶点
pcl::PointCloud<pcl::PointXYZ>::Ptr surface_hull (new pcl::PointCloud<pcl::PointXYZ>);//该点云用于描述凸包形状
hull.reconstruct(*surface_hull, polygons);//计算2D凸包结果
//---------创建CropHull对象，滤波得到2D封闭凸包范围内的点云，此处的维度需要与输入凸包维度一致
pcl::PointCloud<pcl::PointXYZ>::Ptr objects (new pcl::PointCloud<pcl::PointXYZ>);
pcl::CropHull<pcl::PointXYZ> bb_filter;//创建CropHull对象
bb_filter.setDim(2);//设置维度
bb_filter.setInputCloud(cloud);//设置需要滤波的点云
bb_filter.setHullIndices(polygons);//输入封闭多边形的顶点
bb_filter.setHullCloud(surface_hull);//输入封闭多边形的形状
bb_filter.filter(*objects);//执行CropHull滤波，储存结果到objects
cout << objects->size() << endl;
//---------------可视化，从左到右依次是原始点云，封闭2D多边形凸包结果，CropHull滤波结果------------
boost::shared_ptr<pcl::visualization::PCLVisualizer> for_visualizer_v (new pcl::visualization::PCLVisualizer ("crophull display"));
//for_visualizer_v->setBackgroundColor(255,255,255);
//原始点云
int v1(0);
for_visualizer_v->createViewPort (0.0, 0.0, 0.33, 1, v1);
for_visualizer_v->setBackgroundColor (0, 255, 0, v1);
for_visualizer_v->addPointCloud (cloud,"cloud",v1);
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR,255,0,0,"cloud");
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE,3,"cloud");
for_visualizer_v->addPolygon<pcl::PointXYZ>(surface_hull,0,.069*255,0.2*255,"backview_hull_polyline1",v1);
//封闭2D多边形凸包结果
int v2(0);
for_visualizer_v->createViewPort (0.33, 0.0, 0.66, 1, v2);
for_visualizer_v->setBackgroundColor (0, 0, 255, v2);
for_visualizer_v->addPointCloud (surface_hull,"surface_hull",v2);
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR,255,0,0,"surface_hull");
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE,8,"surface_hull");
for_visualizer_v->addPolygon<pcl::PointXYZ>(surface_hull,0,.069*255,0.2*255,"backview_hull_polyline",v2);
//CropHull滤波结果
int v3(0);
for_visualizer_v->createViewPort (0.66, 0.0, 1, 1, v3);
for_visualizer_v->setBackgroundColor (0, 255, 0, v3);
for_visualizer_v->addPointCloud (objects,"objects",v3);
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_COLOR,255,0,0,"objects");
for_visualizer_v->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE,3,"objects");
while (!for_visualizer_v->wasStopped())
{
for_visualizer_v->spinOnce(1000);
}
return 0;
}
三、结果展示
从左到右依次是原始点云，封闭2D多边形凸包结果，CropHull滤波结果
