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ROS image subscriber wont stop subscribing

asked 2019-06-12 03:12:49 -0500

loguna gravatar image

updated 2019-06-12 03:36:07 -0500

gvdhoorn gravatar image


I have a project where this node subscribe to two topics. an image camera topic and a topic that gives input

what i want to do is if the topic input is a '1' than it will not subscribe to the camera, if its a '2', it will subscribe to the camera and take a picture. However, it seems that after i click on '2' and than back to '1', my camera will continue to take pictures.


#!/usr/bin/env python
from __future__ import print_function
import roslib
import sys
import rospy
import cv2
from std_msgs.msg import String, Int32
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError
import os
import numpy as np
import argparse
import time

def test(data):

    bridge = CvBridge()
      cv_image = bridge.imgmsg_to_cv2(data, "bgr8")
    except CvBridgeError as e:
    pub = rospy.Publisher('depthoutput2',String,queue_size=10)

    #cv_image = cv2.imread ('toilet_image_1.jpg')
    image = cv_image
    image = cv2.resize(image, (300,300),fx=0,fy=0, interpolation = cv2.INTER_CUBIC)
    cv2.imwrite('image_photo_taken.jpg', image)
    image = cv2.imread('image_photo_taken.jpg')

    cv2.imshow("Image window",image)

def callback1 (data):  
  movement =

  if movement ==1 :

    print ('stop')
  elif movement ==2 : 

    print('take picture')
    image_sub = rospy.Subscriber("/camera/rgb/image_raw",Image,test)
    print ('error')

def main():
  rospy.init_node ('yolo',anonymous = True)
  rospy.Subscriber('depthoutput', Int32, callback1)

  except KeyboardInterrupt:
    print("Shutting down")


if __name__ == '__main__':
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1 Answer

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answered 2019-06-12 05:59:19 -0500

I think I can see why your code is behaving in this way. While your callback is waiting for the user to press a key the image subscriber is still operating and queuing up messages to process, so that when the callback finishes the next image is immediately processed and so on in a loop.

To be clear, do you want the node to take a single picture when you press 1 or a sequence of pictures until you press 2?

If you just want to take a single picture then you should make your subscriber object image_sub a global initially set to None Then in the image callback call the image_sub.unregister() function so that only a single callback will be executed until the subscriber is re-created again.

If you want to continuously take pictures until 2 is pressed then you'll want to create the subscriber with a queue size of 1:

image_sub = rospy.Subscriber("/camera/rgb/image_raw",Image,test, queue_size=1)

And move the call to image_sub.unregister() into the if movement ==1: case.

Hope this helps.

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If the idea is really to only retrieve a single message from a topic, I would suggest to use rospy.wait_for_message(..). See #q292582 and the other linked Q&As.

gvdhoorn gravatar image gvdhoorn  ( 2019-06-12 06:25:50 -0500 )edit

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Asked: 2019-06-12 03:12:49 -0500

Seen: 787 times

Last updated: Jun 12 '19