ROS service transfer pictures

之前一直用Topicto transfer pictures,近期由于项目需要,需要用service进行图片的传输,Checked a lot of blogs, there are very few detailed explanations,So write a blog record to facilitate follow-up inquiries,Also to help everyone.

topic和serviceThe transfer format for pictures is the same,It's just that the way they communicate is different.

Only the source code is introduced here,对于如何创建service工作空间,How to compile in my上一篇博客中有详细的介绍.

srv文件

img.srv

sensor_msgs/Image image    // 图像转换到sensor_msgs/Image格式进行传输
---
string a
string b

C++版本

ros和opencvSee how to transfer pictures between them：Converting between ROS images and OpenCV images (C++)

客户端程序

client_img.cpp

#include <ros/ros.h>
#include <opencv2/opencv.hpp>
#include <cv_bridge/cv_bridge.h>
#include "learn_service/img.h"

int main(int argc, char** argv)
{
    
	ros::init(argc, argv, "client_img");
	ros::NodeHandle node;

    // 发现/cam服务后,创建一个服务客户端,连接名为/service_img的service
	ros::service::waitForService("/cam");
	ros::ServiceClient img_client = node.serviceClient<learn_service::img>("/cam");

	//读取图片
	cv::Mat image = cv::imread("../data/6.png");
	sensor_msgs::ImagePtr image_srv = cv_bridge::CvImage(std_msgs::Header(), "bgr8", image).toImageMsg();  //Images are converted into message format for transmission

    // 初始化learn_service::img的请求数据
	learn_service::img srv;

	srv.request.image = *image_srv;

    // 请求服务调用
	img_client .call(srv);

	// TO-DO: Process the result of the service call

	return 0;
};

服务端程序

server_img.cpp

#include <ros/ros.h>
#include "learn_service/img.h"
#include <opencv2/opencv.hpp>
#include <cv_bridge/cv_bridge.h>
#include <image_transport/image_transport.h>

// service回调函数,输入参数req,输出参数res
bool cam_result_callback(learn_service::img::Request  &req,
         		 learn_service::img::Response &res)
{
    

    cv_bridge::CvImagePtr cv_ptr;
    //The image has message format to convert intoMat格式
	cv_ptr = cv_bridge::toCvCopy(req.image, sensor_msgs::image_encodings::BGR8);
	cv::imshow("view", cv_ptr->image);
	cv::waitKey(0);

    return true;
}

int main(int argc, char **argv)
{
    
    ros::init(argc, argv, "server_img");
    ros::NodeHandle node;

    // 创建一个名为/cam的server,注册回调函数cam_result_callback
    ros::ServiceServer img_service = node.advertiseService("/cam", cam_result_callback);

    // 循环等待回调函数
    ros::spin();

    return 0;
}

python版本

ros和opencvSee how to transfer pictures between them：Converting between ROS images and OpenCV images (Python)

客户端程序

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys
import rospy
import cv2
from cv_bridge import CvBridge
from sensor_msgs.msg import Image
from learn_service.srv import img, imgRequest

def Img_client():
    # ROS节点初始化
    rospy.init_node('client_img')    
    # 发现/img服务后,创建一个服务客户端,连接名为/img的service
    rospy.wait_for_service('/img')
    bridge = CvBridge()
    #读取图片
    image = cv2.imread('/home/ubuntu/ros_practice/src/learn_service/data/6.png')
    #Convert pictures to message format
    image_message = bridge.cv2_to_imgmsg(image, "bgr8")

    # try:
    img_client = rospy.ServiceProxy('/img', img)
    # 请求服务调用,输入请求数据
    response = img_client(image_message)
    return response.a
	
    # except rospy.ServiceException, e:
    # print "Service call failed: %s"%e

if __name__ == "__main__":
	#服务调用并显示调用结果
    Img_client()

服务端程序

#!/usr/bin/env python3
# -*- coding: utf-8 -*-


import rospy
import cv2
from learn_service.srv import img, imgResponse
from cv_bridge import CvBridge
from sensor_msgs.msg import Image

def ImgCallback(req):
    bridge = CvBridge()
    cv_image = bridge.imgmsg_to_cv2(req.image, "bgr8")
    cv2.imshow("view", cv_image)
    cv2.waitKey(0)
	# 反馈数据
    #return imgResponse("OK1", "OK2")

def img_server():
	# ROS节点初始化
    rospy.init_node('server_img')

	# 创建一个名为/show_person的server,注册回调函数personCallback
    s = rospy.Service('/img', img, ImgCallback)

	# 循环等待回调函数
    print("Ready to show img informtion")
    rospy.spin()

if __name__ == "__main__":
    img_server()