ORB-SLAM2主函數main.cpp

不怕大家笑話，主函數我找了好久才找到，甚至是看完了主要的頭檔案和源檔案後，就非常納悶，主函數呢，跑哪裡去來，最後還是一個個翻，原來是在Examples/Monocular裡。在這呢主要了解下monotmu下的主函數：

#include<iostream>
#include<algorithm>
#include<fstream>
#include<chrono>

#include<opencv2/core/core.hpp>

#include<System.h>

using namespace std;
// 函數聲明，編譯都是從上往下，運作才是從主函數開始，然後一級一級運作，是以要先聲明
void LoadImages(const string &strFile, vector<string> &vstrImageFilenames,
                vector<double> &vTimestamps);

int main(int argc, char **argv)
{
    if(argc != 4)// 确定輸入為4個參數，如下顯示的四個變量
    {
        cerr << endl << "Usage: ./mono_tum path_to_vocabulary path_to_settings path_to_sequence" << endl;
        return 1;
    }

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

    int nImages = vstrImageFilenames.size();

    // Create SLAM system. It initializes all system threads and gets ready to process frames.
    ORB_SLAM2::System SLAM(argv[1],argv[2],ORB_SLAM2::System::MONOCULAR,true);// 執行個體化

    // Vector for tracking time statistics
    vector<float> vTimesTrack;
    vTimesTrack.resize(nImages);

    cout << endl << "-------" << endl;
    cout << "Start processing sequence ..." << endl;
    cout << "Images in the sequence: " << nImages << endl << endl;

    // Main loop
    cv::Mat im;
    for(int ni=0; ni<nImages; ni++)
    {
        // Read image from file
        im = cv::imread(string(argv[3])+"/"+vstrImageFilenames[ni],CV_LOAD_IMAGE_UNCHANGED);
        double tframe = vTimestamps[ni];

        if(im.empty())
        {
            cerr << endl << "Failed to load image at: "
                 << string(argv[3]) << "/" << vstrImageFilenames[ni] << endl;
            return 1;
        }
// 計時，其實不用定義直接用else下的語句就，然後求duration
#ifdef COMPILEDWITHC11
        std::chrono::steady_clock::time_point t1 = std::chrono::steady_clock::now();
#else
        std::chrono::monotonic_clock::time_point t1 = std::chrono::monotonic_clock::now();
#endif

        // Pass the image to the SLAM system
        SLAM.TrackMonocular(im,tframe);

#ifdef COMPILEDWITHC11
        std::chrono::steady_clock::time_point t2 = std::chrono::steady_clock::now();
#else
        std::chrono::monotonic_clock::time_point t2 = std::chrono::monotonic_clock::now();
#endif

        double ttrack= std::chrono::duration_cast<std::chrono::duration<double> >(t2 - t1).count();

        vTimesTrack[ni]=ttrack;

        // Wait to load the next frame
        double T=0;
        if(ni<nImages-1)
            T = vTimestamps[ni+1]-tframe;
        else if(ni>0)
            T = tframe-vTimestamps[ni-1];

        if(ttrack<T)
            usleep((T-ttrack)*1e6);
    }

    // Stop all threads
    SLAM.Shutdown();

    // Tracking time statistics
    sort(vTimesTrack.begin(),vTimesTrack.end());
    float totaltime = 0;
    for(int ni=0; ni<nImages; ni++)
    {
        totaltime+=vTimesTrack[ni];
    }
    cout << "-------" << endl << endl;
    cout << "median tracking time: " << vTimesTrack[nImages/2] << endl;
    cout << "mean tracking time: " << totaltime/nImages << endl;

    // Save camera trajectory
    SLAM.SaveKeyFrameTrajectoryTUM("KeyFrameTrajectory.txt");

    return 0;
}

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())// 讀取每行
    {
        string s;
        getline(f,s);
        if(!s.empty())
        {
            stringstream ss;
            ss << s;
            double t;
            string sRGB;
            ss >> t;
            vTimestamps.push_back(t);// 每行有兩列資料，第一列時間标記
            ss >> sRGB;
            vstrImageFilenames.push_back(sRGB);// 第二列圖檔名
        }
    }
}
           

主函數還是比較簡單的，一時圖像檔案名的處理loadImage()；二是周遊圖像，每個圖像進入system.cpp内運作,單目追蹤TrackMonocular()，儲存關鍵幀軌迹SaveKeyFrameTrajectoryTUM()。

本文是在吳博的基礎上注釋的，是以感謝吳博啊，so nice of you !!!