python - Video stream for ARDRONE - ROS CV Bridge

Question

This is Kathir. While using cv and ros bridge, I am not able to ardrone's camera's output in my computer. Could somebody help me to fix this ? I am not getting any error from the python code.

import roslib
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 image_converter:

 def __init__(self):
   print('Image converter constructor ')
   self.image_pub = rospy.Publisher("image_topic_2",Image,queue_size=1)

   self.bridge = CvBridge()
   self.image_sub = rospy.Subscriber("image_topic",Image,self.callback)

 def callback(self,data):
   try:
     cv_image = self.bridge.imgmsg_to_cv2(data, "bgr8")
   except CvBridgeError as e:
     print(e)

   (rows,cols,channels) = cv_image.shape
   if cols > 60 and rows > 60 :
     cv2.circle(cv_image, (50,50), 10, 255)
   print('Above imshow function')
   cv2.imshow("Image window", cv_image)
   cv2.waitKey(3)

   try:
     self.image_pub.publish(self.bridge.cv2_to_imgmsg(cv_image, "bgr8"))
   except CvBridgeError as e:
     print(e)


def main(args):
 ic = image_converter()
 print('inside main ')
 rospy.init_node('image_converter', anonymous=True)
 try:
   rospy.spin()
 except KeyboardInterrupt:
   print("Shutting down")
 cv2.destroyAllWindows()

if __name__ == '__main__':
   print('Function call started ')
   main(sys.argv)

There is no error in the code. But I am not getting the output of ARDRONE from my laptop ?

Any suggestions are appreciable.