1.说明

通过OpenCV库打开网络摄像头，获取图像，并将其转换为指定Topic的话题发布，项目实现了两台网络摄像头的启动以及话题发布。
注：如需要获取程序中需要的rtsp，即std::string rtsp = “rtsp://192.168.1.101:554/user=admin_password=tlJwpbo6_channel=1_stream=0”; 可参见另一篇文章文章链接

2.部分依赖

1）Ubuntu 18.04
2）ROS版本为melodic
3）OpenCV库版本为 4.5.3

3.关键代码

忽略头文件，主函数只展示关键代码

std::mutex mymutex;
std::atomic_bool isOpen;
cv::VideoCapture capture;

int openCamera(std::string camId, int FPS)
{
	capture.open(camId);
    capture.set(cv::CAP_PROP_FPS, FPS);
	isOpen = capture.isOpened();
    if (isOpen == false)
	{
        std::cout << "Failed to open camera with index " << camId << std::endl;
        return -1;
    }
    std::cout << "Successed open camera with index " << camId << std::endl;
    return 1;
}

int getAndPubImage(int rows, int clos, ros::NodeHandle nh, image_transport::Publisher image_pub, std::string mytopic_name, ros::Rate loop_rate)
{
    cv::Mat frame_image(rows, clos, CV_8UC3);
    image_transport::ImageTransport it(nh);
    image_pub = it.advertise(mytopic_name, 1);
    while (nh.ok())
    {
        capture >> frame_image;
        if (mymutex.try_lock()) 
        {
            sensor_msgs::ImagePtr image_msg = cv_bridge::CvImage(std_msgs::Header(), "bgr8", frame_image).toImageMsg();
            mymutex.unlock();
            image_pub.publish(image_msg);
            loop_rate.sleep();
        }
    }  
}

int main(int argc, char **argv)
{
    // ...................省略部分代码
    //关键代码
	std::string rtsp = "rtsp://192.168.1.101:554/user=admin_password=tlJwpbo6_channel=1_stream=0";
	//  ...................省略部分代码
    ret = openCamera(rtsp, FPS);
    if(ret ==1)
    {
        getAndPubImage(rows, clos, nh, image_pub, topic_name, loop_rate);
    }
    else if(ret == -1)
    {
        return -1;
    }
    capture.release();
    return 0;
}

4.launch文件

<launch> 
    <group ns ="first">
        <param name="cols" type="int" value="1280" />
        <param name="rows" type="int" value="720" />
        <param name="FPS" type="int" value="20" />
        <param name="rate" type="int" value="200" />
        <param name="topic_name" type="string" value="camera/image" />
        <param name="rtsp" type="string" value="rtsp://192.168.1.101:554/user=admin_password=tlJwpbo6_channel=1_stream=0" />

        <node pkg="trans_mat2topic" type="trans_mat2topic" name="trans_mat2topic_first" output="screen" /> 
    </group >

    <group ns ="second">
        <param name="cols" type="int" value="1280" />
        <param name="rows" type="int" value="720" />
        <param name="FPS" type="int" value="20" />
        <param name="rate" type="int" value="200" />
        <param name="topic_name" type="string" value="camera/image" />
        <param name="rtsp" type="string" value="rtsp://192.168.1.121:554/user=admin_password=tlJwpbo6_channel=1_stream=0" />

        <node pkg="trans_mat2topic" type="trans_mat2topic" name="trans_mat2topic_second" output="screen" /> 
    </group >

    <arg name="rviz" default="true" />
    <group if="$(arg rviz)">
        <node launch-prefix="nice" pkg="rviz" type="rviz" name="rviz" args="-d $(find trans_mat2topic)/rviz/showImage.rviz" />
    </group>
</launch>