http://wiki.ros.org/cv_bridge/Tutorials/ConvertingBetweenROSImagesAndOpenCVImagesPython

cv_image = bridge.imgmsg_to_cv2(image_message, desired_encoding="passthrough")
image_message = cv2_to_imgmsg(cv_image, encoding="passthrough")

    """
    passthrough : 입력값 사용 
    mono8: CV_8UC1, grayscale image    
    mono16: CV_16UC1, 16-bit grayscale image    
    bgr8: CV_8UC3, color image with blue-green-red color order    
    rgb8: CV_8UC3, color image with red-green-blue color order    
    bgra8: CV_8UC4, BGR color image with an alpha channel    
    rgba8: CV_8UC4, RGB color image with an alpha channel
    """

Subscriber

#! /usr/bin/python
# Copyright (c) 2015, Rethink Robotics, Inc.

# Using this CvBridge Tutorial for converting
# ROS images to OpenCV2 images
# http://wiki.ros.org/cv_bridge/Tutorials/ConvertingBetweenROSImagesAndOpenCVImagesPython

# Using this OpenCV2 tutorial for saving Images:
# http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_gui/py_image_display/py_image_display.html

# rospy for the subscriber
import rospy
# ROS Image message
from sensor_msgs.msg import Image
# ROS Image message -> OpenCV2 image converter
from cv_bridge import CvBridge, CvBridgeError
# OpenCV2 for saving an image
import cv2

# Instantiate CvBridge
bridge = CvBridge()

def image_callback(msg):
    print("Received an image!")
    try:
        # Convert your ROS Image message to OpenCV2
        cv2_img = bridge.imgmsg_to_cv2(msg, "bgr8")
    except CvBridgeError, e:
        print(e)
    else:
        # Save your OpenCV2 image as a jpeg 
        cv2.imwrite('camera_image.jpeg', cv2_img)

def main():
    rospy.init_node('image_listener')
    # Define your image topic
    image_topic = "/cameras/left_hand_camera/image"
    # Set up your subscriber and define its callback
    rospy.Subscriber(image_topic, Image, image_callback)
    # Spin until ctrl + c
    rospy.spin()

if __name__ == '__main__':
    main()

#!/usr/bin/python
# coding: utf-8


import sys
print(sys.version)


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):
    self.image_pub = rospy.Publisher("image_topic_2",Image)

    self.bridge = CvBridge()
    self.image_sub = rospy.Subscriber("/camera/image_raw",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)

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

if __name__ == '__main__':
    main(sys.argv)