ros2_numpy

This project is a fork of ros_numpy to work with ROS 2. It provides tools for converting ROS messages to and from numpy arrays. In the ROS 2 port, the module has been renamed to ros2_numpy. Users are encouraged to update their application code to import the module as shown below.

ROS 2:

import ros2_numpy as rnp

ROS 1:

import ros_numpy as rnp

Prefacing your calls like rnp.numpify(...) or rnp.msgify(...) should help future proof your codebase while the ROS 1 and ROS 2 ports are API compatible.

The ROS 2 port has been bootstrapped as version 2.0.3. The MAJOR version has been set to 2 to indicate ROS 2 and the MINOR and PATCH versions match the ROS 1 version from which the ROS 2 port was bootstrapped. The reasoning behind this is to allow for creating tags in this fork that can be released into the ROS 2 distribution while not conflicting with existing tags on the upstream repository. A release into Foxy is still pending.

This module contains two core functions:

• arr = numpify(msg, ...) - try to get a numpy object from a message
• msg = msgify(MessageType, arr, ...) - try and convert a numpy object to a message

Currently supports:

• sensor_msgs.msg.PointCloud2 ↔ structured np.array:

   data = np.zeros(100, dtype=[
     ('x', np.float32),
     ('y', np.float32),
     ('vectors', np.float32, (3,))
   ])
   data['x'] = np.arange(100)
   data['y'] = data['x']*2
   data['vectors'] = np.arange(100)[:,np.newaxis]

   msg = ros2_numpy.msgify(PointCloud2, data)
   

   data = ros2_numpy.numpify(msg)
   

• sensor_msgs.msg.Image ↔ 2/3-D np.array, similar to the function of cv_bridge, but without the dependency on cv2
• nav_msgs.msg.OccupancyGrid ↔ np.ma.array
• geometry.msg.Vector3 ↔ 1-D np.array. hom=True gives [x, y, z, 0]
• geometry.msg.Point ↔ 1-D np.array. hom=True gives [x, y, z, 1]
• geometry.msg.Quaternion ↔ 1-D np.array, [x, y, z, w]
• geometry.msg.Transform ↔ 4×4 np.array, the homogeneous transformation matrix
• geometry.msg.Pose ↔ 4×4 np.array, the homogeneous transformation matrix from the origin

Support for more types can be added with:

@ros2_numpy.converts_to_numpy(SomeMessageClass)
def convert(my_msg):
    return np.array(...)

@ros2_numpy.converts_from_numpy(SomeMessageClass)
def convert(my_array):
    return SomeMessageClass(...)

Any extra args or kwargs to numpify or msgify will be forwarded to your conversion function

Future work

• Add simple conversions for:

  • geometry_msgs.msg.Inertia

Changelog for package ros2_numpy

2.0.9 (2023-01-03)

• Fix for numpy 1.24.0
• Contributors: Florian Vahl

2.0.8 (2022-06-12)

• Update for ROS2 Humble (#5)
• Contributors: Sean Kelly

2.0.7 (2022-05-16)

• Remove unneeded array and handle bigendian (#4)
• Contributors: Florian Vahl

2.0.6 (2022-04-15)

• Improve speed of msgify(point_cloud_2_np) by 115x (#3)
• Contributors: Alex Thiel

2.0.5 (2022-02-24)

• Ported to tf_transformations
• Contributors: Tom Panzarella

2.0.4 (2021-11-02)

• Modified transformations.py for quaternion convention (#2)
• Added a test case for the quaternion convention
• Fixed rosdep dependencies in package.xml
• Contributors: Asil Orgen, Tom Panzarella

2.0.3 (2020-07-12)

• Renamed fork to ros2_numpy
• Start tracking changes in CHANGELOG at 2.0.3
• Contributors: Tom Panzarella