使用ros2服务实现人脸检测4-客户端（适合0基础小白）

---

前言

上一篇文章我们完成了人脸检测服务端的编写，给服务端发送请求会收到回复。那么我们现在需要编写一个客户端节点，专门用来发送请求，收回复。

---

一、用到的库

客户端用到的库与服务端基本一致，所以这里就略过。

二、使用步骤

1.在demo_python_service下新建名为detect_node_detect_client_node的python文件

import rclpy
from rclpy.node import Node
from chapt4_interfaces.srv import FaceDetector
import face_recognition
import cv2
from ament_index_python.packages import get_package_share_directory
from cv_bridge import CvBridge
import timeclass FaceDetectClientNode(Node):def __init__(self):super().__init__('face_detect_client_node')self.bridge = CvBridge()self.default_image_path = get_package_share_directory('demo_python_service') + '/resource/test1.jpg'self.get_logger().info(f"人脸检测客户端已启动")self.client = self.create_client(FaceDetector,'face_detect')self.image = cv2.imread(self.default_image_path)def send_request(self):#1.判断服务端是否在线while self.client.wait_for_service(timeout_sec=1.0) is False:self.get_logger().info('等待服务上线！')#2.构造requestrequest = FaceDetector.Request()request.image = self.bridge.cv2_to_imgmsg(self.image)#3.发送请求并等待处理完成future = self.client.call_async(request)# 现在的future并没有包含响应的结果，需要等待服务端处理完成才会把结果放入到future中rclpy.spin_until_future_complete(self,future)response = future.result()self.get_logger().info(f'接受到响应，共检测到有{response.number}张人脸，耗时{response.use_time}s')self.show_response(response)def show_response(self,response):for i in range(response.number):top = response.top[i]right = response.right[i]bottom = response.bottom[i]left = response.left[i]cv2.rectangle(self.image,(left,top),(right,bottom),(255,0,0),4)cv2.imshow('Face Dectect Result',self.image)cv2.waitKey(0)def main():rclpy.init()node = FaceDetectClientNode()node.send_request()rclpy.spin(node)rclpy.shutdown()

2.更改setup.py

在entry_points加入’face_detect_client_node=demo_python_service.face_detect_client_node:main’,

entry_points={'console_scripts': ['learn_face_detect=demo_python_service.learn_face_detect:main','face_detect_node=demo_python_service.face_detect_node:main','face_detect_client_node=demo_python_service.face_detect_client_node:main',],},

保存编译后运行。

二、结果展示

首先运行我们上一章的服务端节点，再运行客户端节点。