如何處理來自 ROS2 的帶有 OpenCV 的圖像消息

Question

我正在嘗試使用來自 ROS2 的 OpenCV 處理圖像消息

我嘗試使用bridge.imgmsg_to_cv2()將 ROS2 Image 轉換為 OpenCV 但它沒有用。 這是我的代碼：

import rclpy
from rclpy.node import Node

from std_msgs.msg import String
from sensor_msgs.msg import Image

import numpy as np
import cv2 as cv
from cv_bridge import CvBridge
bridge = CvBridge()

class MinimalSubscriber(Node):

    def __init__(self):
        ...

    def listener_callback(self, msg):
        self.get_logger().info('1. I heard: "%s"' % msg.width)
        self.get_logger().info('2. I heard: "%s"' % msg.encoding)
        self.cv_image = bridge.imgmsg_to_cv2(msg, 'bgra8')
        self.get_logger().info('3. I heard: "%s"' % self.cv_image)


def main(args=None):
    ...

if __name__ == '__main__':
    main()

使用 output：

[INFO] [1655741136.342080392] [minimal_subscriber]: 1. I heard: "512"
[INFO] [1655741136.342407086] [minimal_subscriber]: 2. I heard: "bgra8"
[INFO] [1655741136.343235582] [minimal_subscriber]: 3. I heard: "[[[180 130  70 255]
  [180 130  70 255]
  [180 130  70 255]
  ...
  [180 130  70 255]
  [180 130  70 255]
  [180 130  70 255]]
.....

誰能幫我？

Answer 1

您嘗試將圖像數據記錄到 ROS 節點控制台，該控制台只能顯示文本。 如果要實際顯示圖像，則需要：

1. 將 CvImage 轉換回 ROS 消息。

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

2. 將圖像消息發布到您選擇的主題。

    try:
      self.image_pub.publish(image_message)
    except CvBridgeError as e:
      print(e)

3. 聆聽您的主題並使用 RQT 或 image_viewer 主題顯示圖像：

   rosrun image_view image_view image:=/your/topic/path

Answer 2

ros2 opencv-python演示

#! /usr/bin/env python3

import rclpy
from rclpy.node import Node 
from sensor_msgs.msg import Image
from cv_bridge import CvBridge
import cv2 
    
class SimplePubSub(Node):
    def __init__(self):
        super().__init__('simple_pub_sub')

        topic_name= 'video_frames'

        self.publisher_ = self.create_publisher(Image, topic_name , 10)
        self.timer = self.create_timer(0.1, self.timer_callback)

        self.cap = cv2.VideoCapture(0)
        self.br = CvBridge()

        self.subscription = self.create_subscription(Image, topic_name, self.img_callback, 10)
        self.subscription 
        self.br = CvBridge()


    def timer_callback(self):
        ret, frame = self.cap.read()     
        if ret == True:
            self.publisher_.publish(self.br.cv2_to_imgmsg(frame))
        self.get_logger().info('Publishing video frame')


    def img_callback(self, data):
        self.get_logger().info('Receiving video frame')
        current_frame = self.br.imgmsg_to_cv2(data)
        cv2.imshow("camera", current_frame)   
        cv2.waitKey(1)


def main(args=None):
    rclpy.init(args=args)
    simple_pub_sub = SimplePubSub()
    rclpy.spin(simple_pub_sub)
    simple_pub_sub.destroy_node()
    rclpy.shutdown()

  
if __name__ == '__main__':
  main()