Collect side-by-side stereovision video and image captures with openCV in C++

main.cpp

//
//  main.cpp
//  OpenCVTest
//
//  Created by ThriveSmart One on 2/29/16.
//  Copyright © 2016 ThriveSmart One. All rights reserved.
//

#include <opencv2/imgcodecs.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/videoio/videoio.hpp>
#include <opencv2/highgui/highgui.hpp>

#include <iostream>
#include <stdio.h>

using namespace cv;
using namespace std;

//hide the local functions in an anon namespace
namespace {
    void help(char** av) {
        cout << "The program captures frames from two cameras connected to your computer." << endl
        << "Usage:\n" << av[0] << " <left device number> <right device number>" << endl
        << "q,Q,esc -- quit" << endl
        << "space   -- save frame" << endl << endl
        << "\tTo capture from a camera pass the device number. To find the device number, try ls /dev/video*" << endl
        << "\texample: " << av[0] << " 0 2" << endl;
    }
    
    int process(VideoCapture& captureL, VideoCapture& captureR) {
        int n = 0;
        char filename[200];
        string window_name = "video | q or esc to quit";
        cout << "press space to save a picture. q or esc to quit" << endl;
        namedWindow(window_name, WINDOW_KEEPRATIO); //resizable window;
        Mat frameL;
        Mat frameR;
        
        for (;;) {
            captureL >> frameL;
            captureR >> frameR;
            if (frameL.empty())
                break;
            
            Mat combinedFrame(frameL.size().height, frameL.size().width+frameR.size().width, frameL.type());
            Mat cfL(combinedFrame, Rect(0, 0, frameL.size().width, frameL.size().height));
            Mat cfR(combinedFrame, Rect(frameL.size().width, 0, frameR.size().width, frameR.size().height));
            frameL.copyTo(cfL);
            frameR.copyTo(cfR);
            
            Mat displayFrame(combinedFrame.size().height / 4, combinedFrame.size().width / 4, combinedFrame.type());
            resize(combinedFrame, displayFrame, displayFrame.size());
            
            imshow(window_name, displayFrame);
            char key = (char)waitKey(30); //delay N millis, usually long enough to display and capture input
            
            switch (key) {
                case 'q':
                case 'Q':
                case 27: //escape key
                    return 0;
                case ' ': //Save an image
                    
                    sprintf(filename,"capture-%.3d.jpg",n++);
                    imwrite(filename,combinedFrame);
                    cout << "Saved " << filename << endl;
                    break;
                default:
                    break;
            }
        }
        return 0;
    }
}

int main(int ac, char** av) {
    
    if (ac != 3) {
        help(av);
        return 1;
    }
    
    std::string argLeft = av[1];
    std::string argRight = av[2];

    VideoCapture captureL(argLeft); //try to open string, this will attempt to open it as a video file or image sequence
    if (!captureL.isOpened()) //if this fails, try to open as a video camera, through the use of an integer param
        captureL.open(atoi(argLeft.c_str()));
    if (!captureL.isOpened()) {
        cerr << "Failed to open the left video device!\n" << endl;
        help(av);
        return 1;
    }
    
    VideoCapture captureR(argRight); //try to open string, this will attempt to open it as a video file or image sequence
    if (!captureR.isOpened()) //if this fails, try to open as a video camera, through the use of an integer param
        captureR.open(atoi(argRight.c_str()));
    if (!captureR.isOpened()) {
        cerr << "Failed to open the right video device!\n" << endl;
        help(av);
        return 1;
    }
    
    return process(captureL, captureR);
}