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Hello subarashi,

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

For checking the, topic uses Rviz: rosrun rviz rviz and subscribe to chatter topic from rviz.

Explanation about what was wrong,

1. You need these lines only if you are printing each frame using imshow.

   k = cv2.waitKey(30) & 0xff if k == 27: break

     cap.release()  
     cv2.destroyAllWindows()
   

2. This should come in a while loop because of each frame you want to be published. In your code nothing will get publish it code will be stuck in a while loop.

   image_message = bridge.cv2_to_imgmsg(img) pub.publish(image_message)

Hello subarashi,

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

For checking the, topic uses Rviz: rosrun rviz rviz and subscribe to chatter topic from rviz.

Explanation about what was wrong,

1. You need these lines only if you are printing each frame using imshow.

   k = cv2.waitKey(30) & 0xff if k == 27: break

     cap.release()  
     cv2.destroyAllWindows()
   

2. This should come in a while loop because of each frame you want to be published. In your code nothing will get publish it code will be stuck in a while loop.

   image_message = bridge.cv2_to_imgmsg(img) bridge.cv2_to_imgmsg(img, encoding="passthrough") pub.publish(image_message)

Hello subarashi,

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

For checking the, topic uses Rviz: rosrun rviz rviz and subscribe to chatter topic from rviz.

Explanation about what was wrong,

1. You need these lines only if you are printing each frame using imshow.

   k = cv2.waitKey(30) & 0xff if k == 27: break

     cap.release()  
     cv2.destroyAllWindows()
   

2. This should come in a while loop because of each frame you want to be published. In your code nothing will get publish it code will be stuck in a while loop.

   image_message = bridge.cv2_to_imgmsg(img, encoding="passthrough") pub.publish(image_message)

Hello subarashi,

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

For checking the, topic uses Rviz: rosrun rviz rviz and subscribe to chatter topic from rviz.

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

Explanation about what was wrong,

1. You need these lines only if you are printing each frame using imshow.

   k = cv2.waitKey(30) & 0xff if k == 27: break

     cap.release()  
     cv2.destroyAllWindows()
   

2. This should come in a while loop because of each frame you want to be published. In your code nothing will get publish it code will be stuck in a while loop.

   image_message = bridge.cv2_to_imgmsg(img, encoding="passthrough") pub.publish(image_message)

Hello subarashi,

For checking the, topic uses use Rviz: rosrun rviz rviz and subscribe to chatter topic from rviz.

#!/usr/bin/env python3
import numpy as np
import cv2
import rospy
from std_msgs.msg import String
from sensor_msgs.msg import Image
import sys
from cv_bridge import CvBridge

bridge = CvBridge()

def cam_test():
      cap = cv2.VideoCapture(-1)
      pub = rospy.Publisher('chatter', Image, queue_size=10)
      rate = rospy.Rate(10)
      while True:
              ret, img = cap.read()
              # gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
              cv2.circle(img,(320,240),15,(0,0,255),2)
              image_message = bridge.cv2_to_imgmsg(img)
              pub.publish(image_message)


if __name__ == '__main__':
       try:
           rospy.init_node('talker', anonymous=True)
           cam_test()
       except rospy.ROSInterruptException:
           pass

Explanation about what was wrong,

1. You need these lines only if you are printing each frame using imshow.

   k = cv2.waitKey(30) & 0xff if k == 27: break

     cap.release()  
     cv2.destroyAllWindows()
   

2. This should come in a while loop because of each frame you want to be published. In your code nothing will get publish it code will be stuck in a while loop.

   image_message = bridge.cv2_to_imgmsg(img, encoding="passthrough") pub.publish(image_message)