はじめに

このライブラリの使い方

github

環境

ubuntu20.04
ROS noetic

install

pip3 install rospy-message-converter

サンプルプログラム

jsonからrosに変換

json_to_ros.py

from rospy_message_converter import json_message_converter

msg_type = "std_msgs/String"
json_msg = '{"data": "Hello, Robot"}'
ros_msg = json_message_converter.convert_json_to_ros_message(msg_type, json_msg)

print(ros_msg)

結果

data: "Hello, Robot"

rosからjsonに変換

std_msgs/String

ros_to_json.py

from rospy_message_converter import json_message_converter
import std_msgs.msg
ros_message = std_msgs.msg.String(data="Hello, Robot")
json = json_message_converter.convert_ros_message_to_json(ros_message)
print(json)

結果

'{"data": "Hello, Robot"}'

geometry_msgs/PoseStamped

ros2json.py

from rospy_message_converter import json_message_converter
from geometry_msgs.msg import *
msg = PoseStamped()
msg.header.frame_id = "map"
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

{"header": {"seq": 0, "stamp": {"secs": 0, "nsecs": 0}, "frame_id": "map"}, "pose": {"position": {"x": 0.0, "y": 0.0, "z": 0.0}, "orientation": {"x": 0.0, "y": 0.0, "z": 0.0, "w": 0.0}}}

geometry_msgs/PointStamped

ros2json.py

from rospy_message_converter import json_message_converter
from geometry_msgs.msg import *
msg = PointStamped()
msg.header.frame_id = "map"
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

{"header": {"seq": 0, "stamp": {"secs": 0, "nsecs": 0}, "frame_id": "map"}, "point": {"x": 0.0, "y": 0.0, "z": 0.0}}

geometry_msgs/Polygon

polygon2json.py

from rospy_message_converter import json_message_converter
import std_msgs.msg
from geometry_msgs.msg import *

msg = Polygon()
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

msg = Polygon()
msg.points.append(Point32(1,2,3))
msg.points.append(Point32(4,5,6))
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

{"points": []}
{"points": [{"x": 1, "y": 2, "z": 3}, {"x": 4, "y": 5, "z": 6}]}

geometry_msgs/PolygonStamped

ps2json.py

from rospy_message_converter import json_message_converter
import std_msgs.msg
from geometry_msgs.msg import *

msg = PolygonStamped()
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

msg = PolygonStamped()
msg.header.frame_id = "map"
msg.polygon.points.append(Point32(1,2,3))
msg.polygon.points.append(Point32(4,5,6))
json = json_message_converter.convert_ros_message_to_json(msg)
print(json)

output

{"header": {"seq": 0, "stamp": {"secs": 0, "nsecs": 0}, "frame_id": ""}, "polygon": {"points": []}}
{"header": {"seq": 0, "stamp": {"secs": 0, "nsecs": 0}, "frame_id": "map"}, "polygon": {"points": [{"x": 1, "y": 2, "z": 3}, {"x": 4, "y": 5, "z": 6}]}}