为什么根据PCL书上移除离群点的代码，pcd文件反而增大了？

Question

以下是pcl第六章点云滤波的算法，移除离群点：
这里用的方法是

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
#include <pcl/filters/statistical_outlier_removal.h>
int
main (int argc, char** argv)
{
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_filtered (new pcl::PointCloud<pcl::PointXYZ>);
  // 填入点云数据
  pcl::PCDReader reader;
  // 把路径改为自己存放文件的路径
  reader.read<pcl::PointXYZ> ("1.pcd", *cloud);
  std::cerr << "Cloud before filtering: " << std::endl;
  std::cerr << *cloud << std::endl;
  // 创建滤波器对象
  pcl::StatisticalOutlierRemoval<pcl::PointXYZ> sor;
  sor.setInputCloud (cloud);
  sor.setMeanK (30);//50个近邻点
  sor.setStddevMulThresh (1.0);//1倍标准方差
  sor.filter (*cloud_filtered);
  std::cerr << "Cloud after filtering: " << std::endl;
  std::cerr << *cloud_filtered << std::endl;

  pcl::PCDWriter writer;
  writer.write<pcl::PointXYZ> ("2.pcd", *cloud_filtered, false);
  sor.setNegative (true);
  sor.filter (*cloud_filtered);
  writer.write<pcl::PointXYZ> ("3.pcd", *cloud_filtered, false);
  return (0);
}

我一个pcd文件滤波前（1.pcd）为80mb，去除后（2.pcd）反而变为了160mb，？？求教各路大神这是什么情况

Answer 1

https://blog.csdn.net/u013351270/article/details/68941821?utm_source=blogxgwz3