Read streaming from camera and show RGB and Gray images

main.cpp

#include <iostream>
#include "opencv2/opencv.hpp"

int main() {
    cv::VideoCapture cam(0);
    if (!cam.isOpened()) {
        throw std::runtime_error("Error");
    }

    cv::namedWindow("Window");
    while (true) {
        cv::Mat frame;
        cam >> frame;
        cv::resize(frame, frame, cv::Size(400, 400));
        cv::imshow("bgr_frame", frame);
        cv::Mat gray_frame;
        cv::cvtColor(frame, gray_frame, CV_BGR2GRAY);
        cv::imshow("gray_frame", gray_frame);
        if (cv::waitKey(30) >= 0) break;
    }
}