tuto_scan_echo

#!/usr/bin/python3
"""Change Lidar message into point cloud object"""
import rclpy
import math
from rclpy.node import Node
from sensor_msgs.msg import LaserScan, PointCloud2
from sensor_msgs_py import point_cloud2
from std_msgs.msg import Header

# Create node
rosNode= None

def scan_callback(scanMsg):
    """receive a lidar message and send a pointcloud message in topic"""
    global rosNode
    obstacles = ranges_to_positions(scanMsg)

    # Sample for the tuto :
    sample = [ [ round(p[0], 2), round(p[1], 2), round(p[2], 2) ] for p in  obstacles[10:20] ]
    # rosNode.get_logger().info( f"\nheader:\n{scanMsg.header}\nnumber of ranges: {len(scanMsg.ranges)}\nSample: {sample}\n" )

    # Publish a msg
    pointCloud = point_cloud2.create_cloud_xyz32(Header(frame_id=scanMsg.header.frame_id), obstacles)
    point_publisher.publish(pointCloud)    


def ranges_to_positions(scan_message: LaserScan) -> list:
    """change a lidar message into a pointcloud message"""
    obstacles= []
    angle= scan_message.angle_min
    for aDistance in scan_message.ranges :
        if 0.1 < aDistance and aDistance < 5.0 :
            aPoint= [
                math.cos(angle) * aDistance,
                math.sin(angle) * aDistance,
                0
            ]
            obstacles.append(aPoint)
        angle+= scan_message.angle_increment
    return obstacles


rclpy.init()
rosNode= Node('scan_interpreter')
# Initialize a subscriber:
rosNode.create_subscription( LaserScan, 'scan', scan_callback, 10)
# Initialize a publisher:
point_publisher = rosNode.create_publisher(PointCloud2, '/scan_points', 10)

while True :
    rclpy.spin_once( rosNode )


rosNode.destroy_node()
rclpy.shutdown()