ROS参数传递

这里只介绍使用roslaunch指令运行launch文件时进行参数传递的情况

0. 常见launch文件写法

//launch文件写法
<launch>
    <node pkg="camera_driver" type="robot_detector" name="cama_detector"  launch-prefix="xterm-e" output="screen"/>
</launch>

• pkg:功能包名
• type:可执行文件名称
• name:节点名字
• launch-prefix:rosrun命令的启动前缀，输出信息在另一个独立终端
• output:输出到屏幕上

1. 使用参数服务器进行参数传递

//launch文件写法
<launch>
    <param name="file_name" type="string" value="/home/nvidia/camera_parameters.yml" />
    <node pkg="camera_driver" type="robot_detector" name="camera_detector"  launch-prefix="xterm-e" output="screen">
        <param name="camera_name" type="string" value="/camera" />
    </node>
    <node pkg="camera_driver" type="robot_detector" name="camerab_detector"  launch-prefix="xterm-e" output="screen" />
</launch>

//CPP文件中的调用方法
std::string camera_name;        //如果该变量为全局变量，将该变量的声明放到全局范围内
ros::param::get("~camera_name", camera_name);           //"~camera_name"表私有参数，在launch文件中，将<param.../>写到<node.../>里面，那么参数就是私有参数
ros::param::get("file_name", filename);                 //"filename"这里使用全局参数，即其他节点也可以使用                            

2. 使用mian参数进行参数传递

//launch文件写法
<launch>
    <param name="file_name" type="string" value="/home/nvidia/camera_parameters.yml" />
    <node pkg="camera_driver" type="robot_detector" name="camera_detector" args="filename" launch-prefix="xterm-e" output="screen" />
</launch>

//CPP文件中的调用方法
ros::init(argc, argv, "robot_detector");
if (argc != 2)
{
    ROS_ERROR("need turtle name as argument");
    return -1;
};
camera_name = argv[1];                          

3. 具体案例解析之main参数传递

• launch文件

 <launch>
    <node pkg="camera_driver" type="camera_sub" name="cameraa_shower" args=" /cameraa" launch-prefix="xterm -e" output="screen" />
    <node pkg="camera_driver" type="camera_sub" name="camerab_shower" args=" /camerab" launch-prefix="xterm -e" output="screen" />
    <node pkg="camera_driver" type="camera_sub" name="camerac_shower" args=" /camerac" launch-prefix="xterm -e" output="screen" />
    <node pkg="camera_driver" type="camera_sub" name="camerad_shower" args=" /camerad" launch-prefix="xterm -e" output="screen" />
 </launch>
 // args文件之前有一个空格，一定不要忘记了
 // pkg是包名，type是可执行文件名称，name是节点名

• CPP文件

#include <ros/ros.h>
#include <opencv2/highgui.hpp>
#include <opencv2/opencv.hpp>
#include <image_transport/image_transport.h>
#include <cv_bridge/cv_bridge.h>


using namespace cv;
using namespace std;

std::string camera_name;            //全局变量

void imageCallback(const sensor_msgs::ImageConstPtr &msg)
{
    try
    {
        cout << camera_name << " : all is ok!!!" << endl;
            imshow(camera_name, cv_bridge::toCvShare(msg, "bgr8")->image);
            waitKey(5);
            cout << "================================================================" << endl;
    }
    catch (cv_bridge::Exception &e)
    {
        ROS_ERROR("Could not convert from '%s' to 'bgr8'.", msg->encoding.c_str());
    }
}

int main(int argc, char **argv)
{
    ros::init(argc, argv, "image_shower");
    if (argc != 2)      //对输入参数数量进行判断
    {
        ROS_ERROR("need turtle name as argument");
        return -1;
    };
    camera_name = argv[1];
    ros::NodeHandle nh;
    namedWindow(camera_name, CV_WINDOW_NORMAL);
    image_transport::ImageTransport it(nh);
    image_transport::Subscriber sub = it.subscribe(camera_name + "/image", 1, imageCallback);
    ros::spin();
    cv::destroyWindow(camera_name);
}

4. 具体案例解析之参数服务器参数传递

• launch文件

 <launch>
    <node pkg="video_driver" type="camera_sub" name="camera_shower" launch-prefix="xterm -e" output="screen">
        <param name="camera_name" type="string" value="/camera" />
    </node>
 </launch>

• CPP文件

#include <ros/ros.h>
#include <opencv2/highgui.hpp>
#include <opencv2/opencv.hpp>
#include <image_transport/image_transport.h>
#include <cv_bridge/cv_bridge.h>


using namespace cv;
using namespace std;

std::string camera_name;

void imageCallback(const sensor_msgs::ImageConstPtr &msg)
{
    try
    {
        cout << camera_name << " : all is ok!!!" << endl;
            imshow(camera_name, cv_bridge::toCvShare(msg, "bgr8")->image);
            waitKey(5);
            cout << "================================================================" << endl;
    }
    catch (cv_bridge::Exception &e)
    {
        ROS_ERROR("Could not convert from '%s' to 'bgr8'.", msg->encoding.c_str());
    }
}

int main(int argc, char **argv)
{
    ros::init(argc, argv, "image_shower");
    ros::param::get("~camera_name", camera_name);               //私有参数解析，也可以通过ros::param::set("~camera_name", camera_name)进行参数设置
    ros::NodeHandle nh;
    namedWindow(camera_name, CV_WINDOW_NORMAL);
    image_transport::ImageTransport it(nh);
    image_transport::Subscriber sub = it.subscribe(camera_name + "/image", 1, imageCallback);
    ros::spin();
    cv::destroyWindow(camera_name);
}