text: #!/usr/bin/env python
  
  import numpy
  
  import cv2
  import cv_bridge
  import rospy
  
  from sensor_msgs.msg import Image
  
  
  class Follower:
      def __init__(self):
          self.bridge = cv_bridge.CvBridge()
          cv2.namedWindow("window", 1)
          self.image_sub = rospy.Subscriber('camera/rgb/image_raw', Image,
                                            self.image_callback)
  
      def image_callback(self, msg):
          image = self.bridge.imgmsg_to_cv2(msg)
          hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
          lower_yellow = numpy.array([50, 50, 170])
          upper_yellow = numpy.array([255, 255, 190])
          mask = cv2.inRange(hsv, lower_yellow, upper_yellow)
          cv2.bitwise_and(image, image, mask=mask)
          cv2.imshow("window", mask)
          cv2.waitKey(3)
  
  
  rospy.init_node('follower')
  follower = Follower()
  rospy.spin()
  