ORB-SLAM2 单目部分技术路线（一）

单目系统构建：

# 本部分代码均位于Examples/Monocular/mono_tum.cc中

1. 数据读入

if(argc != 4)
    {
        cerr << endl << "Usage: ./mono_tum path_to_vocabulary path_to_settings path_to_sequence" << endl;
        return 1;
    }

    // Retrieve paths to images
    vector<string> vstrImageFilenames;
    vector<double> vTimestamps;
    string strFile = string(argv[3])+"/rgb.txt";
    LoadImages(strFile, vstrImageFilenames, vTimestamps);

    int nImages = vstrImageFIlenames.size();

void LoadImages(const string &strFile, vector<string> &vstrImageFilenames, vector<double> &vTimestamps)
{
    ifstream f;
    f.open(strFile.c_str());

    // skip first three lines
    string s0;
    getline(f,s0);
    getline(f,s0);
    getline(f,s0);

    while(!f.eof())
    {
        s