opencv/samples/cpp/starter_video.cpp

/*
* starter_video.cpp
*
*  Created on: Nov 23, 2010
*      Author: Ethan Rublee
*
* A starter sample for using opencv, get a video stream and display the images
* easy as CV_PI right?
*/
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <vector>

using namespace cv;
using namespace std;

//hide the local functions in an anon namespace
namespace {
    void help(char** av) {
        cout << "\nThis program justs gets you started reading images from video\n"
            "Usage:\n./" << av[0] << " <video device number>\n"
            << "\tThis is a starter sample, to get you up and going in a copy pasta fashion\n"
            << "\tThe program captures frames from a camera connected to your computer.\n"
            << "\tTo find the video device number, try ls /dev/video* \n"
            << "\tYou may also pass a video file, like my_vide.avi instead of a device number"
            << endl;
    }

    int process(VideoCapture& capture) {
        string window_name = "video | q or esc to quit";
        cout << "press q or esc to quit" << endl;
        namedWindow(window_name, CV_WINDOW_KEEPRATIO); //resizable window;
        Mat frame;
        for (;;) {
            capture >> frame;
            if (frame.empty())
                continue;
            imshow(window_name, frame);
            char key = (char)waitKey(5); //delay N millis, usually long enough to display and capture input
            switch (key) {
        case 'q':
        case 'Q':
        case 27: //escape key
            return 0;
        default:
            break;
            }
        }
        return 0;
    }

}

int main(int ac, char** av) {

    if (ac != 2) {
        help(av);
        return 1;
    }
    std::string arg = av[1];
    VideoCapture capture(arg); //try to open string, this will attempt to open it as a video file
    if (!capture.isOpened()) //if this fails, try to open as a video camera, through the use of an integer param
        capture.open(atoi(arg.c_str()));
    if (!capture.isOpened()) {
        cerr << "Failed to open a video device or video file!\n" << endl;
        help(av);
        return 1;
    }
    return process(capture);
}