Two ways to read and display point cloud by PCL

Two ways to read point cloud

PCL provides two ways to read and write pcd point clouds. The file format corresponding to PCD (Point Cloud Date, point cloud data) is (*.pcd), which is the official designated format of PCL and has two data storage types , ASCII and Binary .

The point cloud in ASCII format can be viewed directly with Notepad;

Point clouds in Binary format cannot be viewed with Notepad, but it is faster.

Mode 1 PCDReader; PCDWriter

Method 2 loadPCDFile; savePCDFile

1. Read the point cloud from the hard disk

1.1 loadPCDFile

#include <pcl/io/pcd_io.h>

using namespace std;

int main()
{
	//-------------------------------- 从硬盘中读取点云 -----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_in(new pcl::PointCloud<pcl::PointXYZ>); //创建存放读取点云的对象
	if (pcl::io::loadPCDFile("test.pcd", *cloud_in) < 0)
	{
		PCL_ERROR("\a->点云文件不存在！\n");
		system("pause");
		return -1;
	}
	cout << "->加载了 " << cloud_in->points.size() << " 个数据点" << endl;
	//==============================================================================

	return 0;
}

1.2 PCDReader

#include <pcl/io/pcd_io.h>

using namespace std;

int main()
{
	//-------------------------------- 从硬盘中读取点云 -----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_in(new pcl::PointCloud<pcl::PointXYZ>); //创建存放读取点云的对象
	pcl::PCDReader reader;	//定义点云读取对象
	if (reader.read("test.pcd", *cloud_in) < 0)
	{
		PCL_ERROR("\a->点云文件不存在！\n");
		system("pause");
		return -1;
	}
	cout << "->加载了 " << cloud_in->points.size() << " 个数据点" << endl;
	//==============================================================================

	return 0;
}

2. Save the point cloud to the hard disk

2.1 savePCDFile

savePCDFileThere are two commonly used storage formats, one is savePCDFileASCIIand the other is savePCDFileBinary, and you can choose one of the two methods according to your needs.

#include <pcl/io/pcd_io.h>
using namespace std;

int main()
{
	//-------------------------------- 从硬盘中读取点云 -----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_in(new pcl::PointCloud<pcl::PointXYZ>); //存放读取点云的对象
	pcl::PCDReader reader;	//定义点云读取对象
	if (reader.read("test.pcd", *cloud_in) < 0)
	{
		PCL_ERROR("\a->点云文件不存在！\n");
		system("pause");
		return -1;
	}
	cout << "->加载了 " << cloud_in->points.size() << " 个数据点" << endl;
	//==============================================================================
	//------------------------------- 将点云投影至XOY平面 ----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_out(new pcl::PointCloud<pcl::PointXYZ>); //存放投影后的点云

	//定义cloud_out的大小等参数，防止下标越界
	cloud_out->width = cloud_in->width;
	cloud_out->height = 1;
	cloud_out->is_dense = true;
	cloud_out->points.resize(cloud_out->width*cloud_out->height);

	for (size_t i = 0; i < cloud_in->points.size(); i++)
	{
		cloud_out->points[i].x = cloud_in->points[i].x;
		cloud_out->points[i].y = cloud_in->points[i].y;
		cloud_out->points[i].z = 0;
	}
	//-------------------------------- 将点云保存到硬盘 -----------------------------
	///保存为ASICC格式，可以直接用记事本打开
	if (!cloud_out->empty())
	{
		pcl::io::savePCDFileASCII("ASICC_1.pcd", *cloud_out);
		cout << "->(ASICC)保存点数为：" << cloud_out->points.size() << endl;
	}
	else
	{
		PCL_ERROR("\a->保存点云为空！\n");
		system("pause");
		return -1;
	}

	///保存为Binary格式，不可用记事本打开，但更快速。
	if (!cloud_out->empty())
	{
		pcl::io::savePCDFileBinary("Binary_1.pcd", *cloud_out);
		cout << "->(Binary)保存点数为：" << cloud_out->points.size() << endl;
	}
	else
	{
		PCL_ERROR("\a->保存点云为空！\n");
		system("pause");
		return -1;
	}
//==============================================================================
	return 0;
}

2.2 PCDWriter

#include <pcl/io/pcd_io.h>

using namespace std;

int main()
{
	//-------------------------------- 从硬盘中读取点云 -----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_in(new pcl::PointCloud<pcl::PointXYZ>); //存放读取点云的对象
	pcl::PCDReader reader;	//定义点云读取对象
	if (reader.read("test.pcd", *cloud_in) < 0)
	{
		PCL_ERROR("\a->点云文件不存在！\n");
		system("pause");
		return -1;
	}
	cout << "->加载了 " << cloud_in->points.size() << " 个数据点" << endl;
//==============================================================================
	//------------------------------- 将点云投影至XOY平面 ----------------------------
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_out(new pcl::PointCloud<pcl::PointXYZ>); //存放投影后的点云

	//定义cloud_out的大小等参数，防止下标越界
	cloud_out->width = cloud_in->width;
	cloud_out->height = 1;
	cloud_out->is_dense = true;
	cloud_out->points.resize(cloud_out->width*cloud_out->height);

	for (size_t i = 0; i < cloud_in->points.size(); i++)
	{
		cloud_out->points[i].x = cloud_in->points[i].x;
		cloud_out->points[i].y = cloud_in->points[i].y;
		cloud_out->points[i].z = 0;
	}
	//-------------------------------- 将点云保存到硬盘 -----------------------------
	pcl::PCDWriter writer;
	///保存为ASICC格式，可以直接用记事本打开
	if (!cloud_out->empty())
	{
		writer.write("ASICC_2.pcd", *cloud_out,false);	//默认false(可以不写)，保存为ASICC格式
		cout << "->(ASICC)保存点数为：" << cloud_out->points.size() << endl;
	}
	else
	{
		PCL_ERROR("\a->保存点云为空！\n");
		system("pause");
		return -1;
	}
	///保存为Binary格式，不可用记事本打开，但更快速。
	if (!cloud_out->empty())
	{
		writer.write("Binary_2.pcd", *cloud_out, true);	//true，保存为Binary格式
		cout << "->(Binary)保存点数为：" << cloud_out->points.size() << endl;
	}
	else
	{
		PCL_ERROR("\a->保存点云为空！\n");
		system("pause");
		return -1;
	}
//==============================================================================
	return 0;
}

3. The difference between the two methods of reading and writing point clouds

The difference between PCDReader and loadPCDFile

//PCDReader
pcl::PCDReader reader;
reader.read("1.pcd",*cloud);

//loadPCDFile
pcl::io::loadPCDFile("1.pcd",*cloud);

• The difference between PCDWriter and savePCDFile

//PCDWriter
pcl::PCDWriter writer;
writer.write("1.pcd",*cloud);

//savePCDFile
pcl::io::savePCDFileBinary("1.pcd",*cloud);

Similarly, the savePCDFile function is also implemented by calling PCDWriter

//savePCDFile 
template<typename PointT> inline int
    savePCDFile (const std::string &file_name, const pcl::PointCloud<PointT> &cloud, bool binary_mode = false)
    {
      PCDWriter w;
      return (w.write<PointT> (file_name, cloud, binary_mode));
    }
//savePCDFileASCII 
template<typename PointT> inline int
    savePCDFileASCII (const std::string &file_name, const pcl::PointCloud<PointT> &cloud)
    {
      PCDWriter w;
      return (w.write<PointT> (file_name, cloud, false));
    }
//savePCDFileBinary
template<typename PointT> inline int
    savePCDFileBinary (const std::string &file_name, const pcl::PointCloud<PointT> &cloud)
    {
      PCDWriter w;
      return (w.write<PointT> (file_name, cloud, true));
    }