[Python OpenCV ROS] cv.cap으로 딴 이미지 compressedImage msg로 publish하기

-> Thread에서 opencv cap 함수로 webcam 혹은 usbcam 이미지 프레임별로 캡쳐해서 

-> ROS topic 중에서 compressedimage msg로 publish하기

-> Thread Keyboard Interrupt 넣어서 안전하게 끄기

#!/usr/bin/env python
import rospy
import roslib
import sys, time
import cv2 
import threading
from sensor_msgs.msg import CompressedImage

def TVStart(data) :
	img_thread = DroneTV()
	try:
		img_thread.daemon=True
		img_thread.start()
	except KeyboardInterrupt :
		img_thread.stop()
		print("Shut down...")

class DroneTV(threading.Thread) :
	def __init__(self) :
		threading.Thread.__init__(self)
		global thread_running
		self.cap = cv2.VideoCapture(0) #now web cam
		thread_running = True


	def run(self) :
		global thread_running
		msg  = CompressedImage()
		while thread_running :
			b, frame = self.cap.read()
			if b:
				msg.header.stamp = rospy.Time.now()
				msg.format =  "jpeg"
				encode_param=[int(cv2.IMWRITE_JPEG_QUALITY),10]
				msg.data = np.array(cv2.imencode('.jpg', frame, encode_param)[1]).tostring()
				pub_compressed_img.publish(msg)
			else : 
				pass

	def stop(self) :
		thread_running = False
		self.quit()
		self.wait(5000)

TVStart()
pub_compressed_img = rospy.Publisher('/tello_img/image_raw/compressed', CompressedImage,  queue_size = 1)