Combining two nodes using a launch-file , and cv2.imwrite() not working as a result [closed]

edit

(I am using ros melodic, on ubuntu 18.04, and turtlebot-2)

I have two python files goforward.py: which keeps moving the turtlebot forward untill we terminate using ctrl+C, and take_photo_mod.py, which uses the camera to take photos at 1 second intervals, and saves them to the cwd (and keeps running until we terminate using ctrl+C).

goforward.py

#!/usr/bin/env python
import rospy
from geometry_msgs.msg import Twist

class GoForward():
    def __init__(self):
        # initiliaze
        rospy.init_node('GoForward', anonymous=False)

    # tell user how to stop TurtleBot
    rospy.loginfo("To stop TurtleBot CTRL + C")

        # What function to call when you ctrl + c    
        rospy.on_shutdown(self.shutdown)

    # Create a publisher which can "talk" to TurtleBot and tell it to move
        # Tip: You may need to change cmd_vel_mux/input/navi to /cmd_vel if you're not using TurtleBot2
        self.cmd_vel = rospy.Publisher('cmd_vel_mux/input/navi', Twist, queue_size=10)

    #TurtleBot will stop if we don't keep telling it to move.  How often should we tell it to move? 10 HZ
        r = rospy.Rate(10);

        # Twist is a datatype for velocity
        move_cmd = Twist()
    # let's go forward at 0.2 m/s
        move_cmd.linear.x = 0.2
    # let's turn at 0 radians/s
    move_cmd.angular.z = 0

    # as long as you haven't ctrl + c keeping doing...
        while not rospy.is_shutdown():
        # publish the velocity
            self.cmd_vel.publish(move_cmd)
        # wait for 0.1 seconds (10 HZ) and publish again
            r.sleep()


    def shutdown(self):
        # stop turtlebot
        rospy.loginfo("Stop TurtleBot")
    # a default Twist has linear.x of 0 and angular.z of 0.  So it'll stop TurtleBot
        self.cmd_vel.publish(Twist())
    # sleep just makes sure TurtleBot receives the stop command prior to shutting down the script
        rospy.sleep(1)

if __name__ == '__main__':
    try:
        GoForward()
    except:
        rospy.loginfo("GoForward node terminated.")

take_photo_mod.py

#!/usr/bin/env python
from __future__ import print_function
import sys
import rospy
import cv2
from std_msgs.msg import String
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError

class TakePhoto:
    def __init__(self):

        self.bridge = CvBridge()
        self.image_received = False

        # Connect image topic
        img_topic = "/camera/rgb/image_raw"
        self.image_sub = rospy.Subscriber(img_topic, Image, self.callback)

        # Allow up to one second to connection
        rospy.sleep(1)

    def callback(self, data):

        # Convert image to OpenCV format
        try:
            cv_image = self.bridge.imgmsg_to_cv2(data, "bgr8")
        except CvBridgeError as e:
            print(e)

        self.image_received = True
        self.image = cv_image

    def take_picture(self, img_title):
        if self.image_received:
            # Save an image
            cv2.imwrite(img_title, self.image)
            rospy.loginfo("received")

            return True
        else:
            return False

if __name__ == '__main__':

    # Initialize
    rospy.init_node('take_photo', anonymous=False)
    camera = TakePhoto()

    # Take a photo

    # Use '_image_title' parameter from command line
    # Default value is 'photo.jpg'
    while not rospy.is_shutdown():

        img_title = rospy.get_param('~image_title', 'photo1.jpg')

        if camera.take_picture(img_title):
            rospy.loginfo("Saved image " + img_title)
        else:
            rospy.loginfo("No images received")

        # Sleep to give the last log messages time to be sent
        rospy.sleep(1)

These two programs individually, are running flawlessly. I can see the turtlebot moving in the environment. I can ... (more)