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Ok as many people has viewed this so i thought of answering my own question. I solved it like this.

import message_filters
import cv2
import rospy
from cv_bridge import CvBridge

def callback(rgb_msg, camera_info):
   rgb_image = CvBridge().imgmsg_to_cv2(rgb_msg, desired_encoding="rgb8")
   camera_info_K = np.array(camera_info.K).reshape([3, 3])
   camera_info_D = np.array(camera_info.D)
   rgb_undist = cv2.undistort(rgb_image, camera_info_K, camera_info_D)

if __name__ == '__main__':
   rospy.init_node('my_node', anonymous=True)
   image_sub = message_filters.Subscriber('/ardrone/front/image_raw', Image)
   info_sub = message_filters.Subscriber('/ardrone/front/camera_info', CameraInfo)
   ts = message_filters.ApproximateTimeSynchronizer([image_sub, info_sub], 10, 0.2)
   ts.registerCallback(callback)
   rospy.spin()

So my problem was how to subscribe on two different topics and use their data for further processing. "message_filters.ApproximateTimeSynchronizer" synchronized the incoming messages according to the time stamp with each message being received and with "ts.registerCallback(callback)" i was able to use both subscribed messages together for further processing in callback function.