[opencv450 samples] create image list yaml

/*this creates a yaml or xml list of files from the command line args
 */

#include "opencv2/core.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include <string>
#include <iostream>

using std::string;
using std::cout;
using std::endl;

using namespace cv;

static void help(char** av)
{
    cout << "\nThis creates a yaml or xml list of files from the command line args\n"
        " This will be from the command line  args  Create a  yaml  or  xml  File list \n"
        "usage:\n./" << av[0] << " imagelist.yaml *.png\n"
        << "Try using different extensions.(e.g. yaml yml xml xml.gz etc...)\n"
        << "This will serialize this list of images or whatever with opencv's FileStorage framework" << endl;
}

int main(int ac, char** av)
{
    cv::CommandLineParser parser(ac, av, "{help h||}{@output||}");
    if (parser.has("help"))
    {
        help(av);
        return 0;
    }
    string outputname = parser.get<string>("@output");// Output file name 

    if (outputname.empty())
    {
        help(av);
        return 1;
    }

    Mat m = imread(outputname); // Check whether the output is an image  -  To prevent from covering ！ check if the output is an image - prevent overwrites!
    if (!m.empty()) {// Failure ！  Please specify an output file , Don't overwrite your image 
        std::cerr << "fail! Please specify an output file, don't want to overwrite you images!" << endl;
        help(av);
        return 1;
    }

    FileStorage fs(outputname, FileStorage::WRITE);// File store write 
    fs << "images" << "[";
    for (int i = 2; i < ac; i++) {// Traverse all image names 
        fs << string(av[i]);
    }
    fs << "]";
    return 0;
}