code: #读写点云，网格，图片文件
  
  import numpy as np
  import open3d as o3d
  pcd=o3d.io.read_point_cloud("data/rs1.pcd")
  
  print(pcd)      #打印点云数量
  
  #可视化一下
  o3d.visualization.draw_geometries([pcd])
   
  #下采样
  downpcd = pcd.voxel_down_sample(voxel_size=0.05)
  o3d.visualization.draw_geometries([downpcd])
   
  #计算法向量
  downpcd.estimate_normals(search_param=o3d.geometry.KDTreeSearchParamHybrid(radius=0.1, max_nn=30))
  o3d.visualization.draw_geometries([downpcd])
   
  #原来这样获取
  print("Print a normal vector of the 0th point")
  print(downpcd.normals[0])
  print("Print the normal vectors of the first 10 points")
  print(np.asarray(downpcd.normals)[:10, :])
  
  o3d.io.write_point_cloud("data/copy_rs1.pcd",pcd)
  
  #打印网格
  mesh=o3d.io.read_triangle_mesh("data/Box.stl")
  o3d.visualization.draw_geometries([mesh])
  print(mesh)
  o3d.io.write_triangle_mesh("data/copy_box.stl",mesh)
  
  #读写图像
  img=o3d.io.read_image('data/image.jpg')
  print(img)
  o3d.io.write_image("data/copy_img.jpg",img)
  
apis: numpy.asarray