Can't convert Images from a rosbag
awesomebytes opened this issue · 2 comments
awesomebytes commented
If reading messages from a rosbag one gets an error like:
ValueError: Unable to convert message _sensor_msgs__Image - only supports Numpy_sensor_msgs__Image, Numpy_geometry_msgs__Transform, Numpy_nav_msgs__OccupancyGrid, Numpy_sensor_msgs__PointField[], Transform, PointField[], Image, Numpy_geometry_msgs__Quaternion, OccupancyGrid, PointCloud2, Numpy_geometry_msgs__Point, Pose, Point, Numpy_geometry_msgs__Vector3, Numpy_geometry_msgs__Pose, Numpy_sensor_msgs__PointCloud2, Vector3, Quaternion
That's because
In [1]: from sensor_msgs.msg import Image
In [2]: img = Image()
In [3]: img.__class__
Out[3]: sensor_msgs.msg._Image.Image
In [4]: from rosbag import Bag
In [5]: b = Bag('poc_bag.bag')
In [6]: r = b.read_messages(topics=['/pepper/camera/depth/image_raw'] )
In [7]: topic, msg, time = r.next()
In [8]: msg.__class__
Out[8]: tmpldS_vh._sensor_msgs__Image
In [13]: img.__class__.__name__
Out[13]: 'Image'
In [14]: msg.__class__.__name__
Out[14]: '_sensor_msgs__Image'
From a rosbag the messages don't seem to have the proper type (I guess it has something to do with the way messages are stored).
rarmstrong22 commented
I've run into this, too. Appears to be a rosbag issue, not a ros_numpy
issue. Also plays havoc with pickle
. I found that I could work around this by inserting the correct __class__
when loading from a rosbag. Lame, but it works for my need:
for msg in msgs:
if msg.topic == odom_topic:
msg.message.__class__ = nav_msgs.msg._Odometry.Odometry
odom_msgs.append(msg.message)
if msg.topic == scan_topic:
msg.message.__class__ = sensor_msgs.msg._PointCloud2.PointCloud2
scan_msgs.append(msg.message)
manasrda commented
Based on the answer by rarmstrong22.
For anyone searching for a quick working solution. In case you are sure it is a ROS Image message but it still throws this error.
This worked for me:
import ros_numpy
import sensor_msgs
def get_img_from_ros_image_msg(msg):
""" Returns image as a numpy array.
Note: can be used with any topic of message type 'sensor_msgs/Image'
"""
msg.__class__ = sensor_msgs.msg.Image
return ros_numpy.numpify(msg)
img_array = get_img_from_ros_image_msg(msg)