ROS msg including image and related variables related to that image

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I need to create a publisher which can publish an image along with a few strings, integers and arrays containing different information about the image (like number of objects, bounding boxes, name of the objects inside image etc).

Up until now, I am successful to publish image using the following command:

  pub_msg = bridge.cv2_to_imgmsg(img, "bgr8")
  pub.publish(pub_msg)

But I dont understand how to incorporate rest of the data with this image. If I create custom ROS msg, how to add all these information variables along with and image data. Please guide me or suggest me some tutorial where I can get some related help.