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Hi! I am subscribing to a data of Type: sensor_msgs/PointCloud2. How do I save he point cloud data in a python file. How do I convert it to ROS daa. Please share links of tutorial if any. I am not able to find one.
Have you heard of open3d ?, that is a Python libabry which can help you save cloud with popular formats(e.g .ply).
lets say you have pointcloud2 topic and you want to read and save the Pointcloud
from sensor_msgs.msg import PointCloud2, PointField
import numpy as np
import open3d as o3d
import sensor_msgs.point_cloud2 as pc2
import ctypes
import struct
def callback(self, ros_point_cloud):
xyz = np.array([[0,0,0]])
rgb = np.array([[0,0,0]])
#self.lock.acquire()
gen = pc2.read_points(ros_point_cloud, skip_nans=True)
int_data = list(gen)
for x in int_data:
test = x[3]
# cast float32 to int so that bitwise operations are possible
s = struct.pack('>f' ,test)
i = struct.unpack('>l',s)[0]
# you can get back the float value by the inverse operations
pack = ctypes.c_uint32(i).value
r = (pack & 0x00FF0000)>> 16
g = (pack & 0x0000FF00)>> 8
b = (pack & 0x000000FF)
# prints r,g,b values in the 0-255 range
# x,y,z can be retrieved from the x[0],x[1],x[2]
xyz = np.append(xyz,[[x[0],x[1],x[2]]], axis = 0)
rgb = np.append(rgb,[[r,g,b]], axis = 0)
out_pcd = o3d.geometry.PointCloud()
out_pcd.points = o3d.utility.Vector3dVector(xyz)
out_pcd.colors = o3d.utility.Vector3dVector(rgb)
o3d.io.write_point_cloud("/home/atas/cloud.ply",out_pcd)
I have used this code before and it works but you may adjust some parts of the code for your needs
This is good solution. However, when I tried running it, it took too long to save only one pcl/pcd file.
Considering that the average point number in a PointCloud message is usually too big, and we already know it from the length of int_data array, we can eliminate the np.append() operations by pre-allocating the space for numpy arrays as below:
xyz = np.empty((len(int_data), 3))
rgb = np.empty((len(int_data), 3))
Then we can assign each point in the loop with an index. E.g. xyz[idx] = x[:3]
This way the function completes way faster.
Asked: 2017-02-22 18:35:28 -0600
Seen: 5,837 times
Last updated: Apr 12 '20
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Support for PCL datatypes in Python is rather thin. If you search around, you'll find a few people who have written some conversion methods themselves (ie: PCL -> numpy) but it's all unofficial. PCL currently works best from C++ I'm afraid.