ros_numpy

Tools for converting ROS messages to and from numpy arrays. Contains two 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 = ros_numpy.msgify(PointCloud2, data)

   data = ros_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:

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

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

Any extra args or kwargs to

numpify

msgify

Future work

• Add simple conversions for:

  • geometry_msgs.msg.Inertia