Created
April 18, 2020 04:08
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Node to convert a ROS Image topic publisher from RGB to grayscale (rgb or bgr to mono8) using opencv and cv_bridge
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#!/usr/bin/env python | |
import sys | |
import rospy | |
from sensor_msgs.msg import Image | |
from cv_bridge import CvBridge | |
import cv2 | |
""" | |
Node to transform an input Image topic into | |
an output grayscale Image topic. | |
Author: Sammy Pfeiffer <Sammy.Pfeiffer at student.uts.edu.au> | |
""" | |
class GrayScaler(object): | |
def __init__(self, name_topic_in, name_topic_out): | |
self.cv_bridge = CvBridge() | |
rospy.loginfo("Converting Images from topic " + name_topic_in + | |
" to grayscale, output topic: " + name_topic_out) | |
self.pub = rospy.Publisher(name_topic_out, Image, queue_size=5) | |
self.sub = rospy.Subscriber( | |
name_topic_in, Image, self.image_cb, queue_size=5) | |
def image_cb(self, img_msg): | |
# Transform to cv2/numpy image | |
img_in_cv2 = self.cv_bridge.imgmsg_to_cv2( | |
img_msg, desired_encoding='passthrough') | |
# Transform to grayscale, | |
# available encodings: http://docs.ros.org/jade/api/sensor_msgs/html/image__encodings_8h_source.html | |
if "rgb" in img_msg.encoding: | |
gray_img = cv2.cvtColor(img_in_cv2, cv2.COLOR_RGB2GRAY) | |
elif "bgr" in img_msg.encoding: | |
gray_img = cv2.cvtColor(img_in_cv2, cv2.COLOR_BGR2GRAY) | |
# Transform back to Image message | |
gray_img_msg = self.cv_bridge.cv2_to_imgmsg( | |
gray_img, encoding="mono8") | |
self.pub.publish(gray_img_msg) | |
if __name__ == '__main__': | |
argv = rospy.myargv(sys.argv) | |
if len(argv) != 3: | |
print("Usage:") | |
print(argv[0] + " name_topic_in name_topic_out") | |
print("Converts a RGB/BGR name_topic_in Image topic into a Grayscale name_topic_out Image topic") | |
exit(0) | |
rospy.init_node("image_to_grayscale", anonymous=True) | |
gs = GrayScaler(argv[1], argv[2]) | |
rospy.spin() |
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