C++主函数参数

学习C++主函数的参数输入，用于从command line中读取参数，下面以读取视频文件为例进行说明

#include <iostream>
#include <fstream>
#include <string>
#include <opencv2/opencv.hpp>

int main(int argc, char* argv[]) {
    if (argc != 2) {
        std::cerr << "usage: play_video <video_path>" << std::endl;
        return -1;
    }

    std::string video_path = argv[1];
    // check video file exist or not
    std::ifstream video_file(video_path);
    if (!video_file.is_open()) {  // 同video_file.fail()
        std::cerr << "Video file not exist!" << std::endl;
        return -1;
    }

    // VideoCapture
    cv::VideoCapture cap(video_path);
    if (!cap.isOpened()) {
        std::cerr << "Open Video Failed!" << std::endl;
        return -1;
    }

    // Video Processing code here
    cv::Mat frame;
    while(1) {
        cap >> frame;
        if(frame.empty())
            break;

        cv::imshow("frame", frame);
        cv::waitKey(25);
}

    return 0;
}

• Argparse for modern C++: https://github.com/p-ranav/argparse
• Lightweight C++ command line option parser: https://github.com/jarro2783/cxxopts