ROS Resources: Documentation | Support | Discussion Forum | Index | Service Status | ros @ Robotics Stack Exchange
Ask Your Question

Problem Listener with [closed]

asked 2017-04-12 09:35:38 -0500

icarold gravatar image

Good morning people

I did a listener for the camera/image_raw node republish (camera/image_test, but the following error appears: Client [/ QR_Listener_5598_1492006578702] wants topic /camera/image_test to have datatype/md5sum [std_msgs /String/992ce8a1687cec8c8bd883ec73ca41d1], but our version has [sensor_msgs/Image/060021388200f6f0f447d0fcd9c64743]. Dropping connection.

Follow the listener code:

#!/usr/bin/env python

import rospy
import cv2
import zbar

from std_msgs.msg import String
from PIL import Image

def callback(data):
    scanner = zbar.ImageScanner()

    while not rospy.is_shutdown():
        ret, output =

        if not ret:

        gray = cv2.cvtColor(output, cv2.COLOR_BGR2GRAY, dstCn=0)
        pil = Image.fromarray(gray)
        width, height = pil.size
        raw = pil.tobytes()
        image = zbar.Image(width, height, 'Y800', raw)

        qrc = None

        for symbol in image:
            print '"%s"' %
            qrc =


        cv2.imshow("#Qr Code", output)

        if qrc != None:
            rospy.loginfo(rospy.get_caller_id() + "Qr Code %s:",

def listener():
    rospy.init_node('QR_Listener', anonymous=True)

    rospy.Subscriber("/camera/image_test", String, callback)


if __name__ == '__main__':

    except rospy.ROSInterruptException:
edit retag flag offensive reopen merge delete

Closed for the following reason the question is answered, right answer was accepted by NEngelhard
close date 2017-04-14 09:59:29.534867

1 Answer

Sort by » oldest newest most voted

answered 2017-04-12 10:41:49 -0500

NEngelhard gravatar image

updated 2017-04-13 01:44:51 -0500

The answer is already in the error message: You create a std_msgs::String subscriber to listen to an sensor_msgs::Image message.

So it should be

from sensor_msgs.msg import Image

 rospy.Subscriber("/camera/image_test", Image, callback)
edit flag offensive delete link more


Many thanks, my friend !! Lack of attention to mine. I'll test here

icarold gravatar image icarold  ( 2017-04-12 11:07:12 -0500 )edit

The command did not work:

from visualization_msgs.msg import Image
ImportError: cannot import name Image
icarold gravatar image icarold  ( 2017-04-12 20:47:35 -0500 )edit

@icarold You should not add an answer that is not really an answer. If you need to add information, please edit your original question. I've moved your answer to be a comment.

jarvisschultz gravatar image jarvisschultz  ( 2017-04-12 22:47:17 -0500 )edit

The error described in your comment is because the visualization_msgs package doesn't have a message called Image (it has ImageMarker). My guess is that you are actually looking for the sensor_msgs/Image message type.

jarvisschultz gravatar image jarvisschultz  ( 2017-04-12 22:49:07 -0500 )edit

sorry, it's of course in sensor_msgs, fixed it

NEngelhard gravatar image NEngelhard  ( 2017-04-13 01:46:11 -0500 )edit

I used the sensor_msgs.msg import image as suggested, but now it is giving no error

File "/home/icaro/catkin_ws/src/tcc/scripts/", line 14, in callback
     Ret, output = ()
AttributeError: 'Image' object has no attribute 'read'
icarold gravatar image icarold  ( 2017-04-13 09:32:39 -0500 )edit

If I take the read() error in the:

ret, output = data
TypeError: 'Image' object is not iterable
icarold gravatar image icarold  ( 2017-04-13 09:33:05 -0500 )edit

why do you think that an Image-object has a read-function?

NEngelhard gravatar image NEngelhard  ( 2017-04-13 15:15:23 -0500 )edit

Question Tools

1 follower


Asked: 2017-04-12 09:35:38 -0500

Seen: 1,059 times

Last updated: Apr 13 '17