I am trying to convert PointCloud2 data to numpy array.

I am converting it with package: sensor_msgs_py.pointcloud2 using the method: read_points

I always get an error that Cloud is not a sensor_msgs.msg.PointCloud2 but I am sure that the data I am giving to function are PoinCloud2 type. I am getting data directly by subscribing to this topic: /D435_1/depth/color/points [sensor_msgs/msg/PointCloud2] 1 publisher

Camera I am using is: Realsense D435


from rclpy.node import Node
from sensor_msgs.msg import PointCloud2
from std_msgs.msg import Header
import open3d as o3d
import numpy as np
import sensor_msgs_py.point_cloud2 as pc2
import sensor_msgs_py.numpy_compat as nc
import cv2

class MySubscriber(Node):
    def __init__(self):
        self.subscription = None
        self.subscription = self.create_subscription(PointCloud2, '/D435_1/depth/color/points', self.callback, 10)      
        self.camera_width = 848
        self.camera_height = 480

    def callback(self, msg: PointCloud2):
        self.get_logger().info('Received PointCloud2 message')
        self.point_cloud_data = msg.data
        points = self.convert_point_cloud_msg_to_numpy(self.point_cloud_data)
    def convert_point_cloud_msg_to_numpy(self, data: PointCloud2):
        if self.point_cloud_data is not None:
            print('test message 1')
            # Parse the PointCloud2 message
            gen = pc2.read_points(data, field_names=("x", "y", "z"), skip_nans=True)
            print('test message 2')

            # Convert the point cloud to a numpy array
            points_numpy = np.array(list(data), dtype=np.float32)

            return points_numpy

def main():
    subscriber = MySubscriber()

if __name__ == '__main__':

Error message: File "/opt/ros/humble/lib/python3.10/site-packages/sensor_msgs_py/point_cloud2.py", line 88, in read_points assert isinstance(cloud, PointCloud2),
AssertionError: Cloud is not a sensor_msgs.msg.PointCloud2


1 Answer 1


Figured it out:

you should pass the whole msg data you get from the topic to the read_points function, not just msg.data data.


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