Opencv4.0：遍历Mat图像空间、读取摄像头

#include "opencv2/opencv.hpp"
using namespace cv;
#pragma comment(lib, "opencv_calib3d340d.lib")
#pragma comment(lib, "opencv_core340d.lib")
#pragma comment(lib, "opencv_dnn340d.lib")
#pragma comment(lib, "opencv_features2d340d.lib")
#pragma comment(lib, "opencv_flann340d.lib")
#pragma comment(lib, "opencv_highgui340d.lib")
#pragma comment(lib, "opencv_imgcodecs340d.lib")
#pragma comment(lib, "opencv_imgproc340d.lib")
#pragma comment(lib, "opencv_ml340d.lib")
#pragma comment(lib, "opencv_objdetect340d.lib")
#pragma comment(lib, "opencv_photo340d.lib")
#pragma comment(lib, "opencv_shape340d.lib")
#pragma comment(lib, "opencv_stitching340d.lib")
#pragma comment(lib, "opencv_superres340d.lib")
#pragma comment(lib, "opencv_video340d.lib")
#pragma comment(lib, "opencv_videoio340d.lib")
#pragma comment(lib, "opencv_videostab340d.lib")

int main()
{
    //显示图片
    Mat image = imread("test.png");
    namedWindow("window");
    imshow("window", image);

    //遍历Mat图像空间
    Mat mat(500, 300, CV_8UC3);
    //mat.create(500, 300, CV_8UC3);
    int size = mat.rows*mat.cols*mat.elemSize();
    int esize = mat.elemSize();
    for (int i = 0; i < size; i += esize)
    {
        mat.data[i] = 0;//B
        mat.data[i+1] = 255;//G
        mat.data[i+2] = 0;//R
    }
    namedWindow("Mat");
    imshow("Mat", mat);

    //读取摄像头
    VideoCapture cam;
    bool res = cam.open("rtsp://184.72.239.149/vod/mp4://BigBuckBunny_175k.mov");
    //bool res = cam.open(0);
    Mat capture;
    namedWindow("Cap");
    if (cam.isOpened())
    {
        while (true)
        {
            //cam.read(capture);
            if (!cam.grab())//读取并解码
                continue;
            if(!cam.retrieve(capture))//YUV转RGB
                continue;
            imshow("Cap", capture);
            waitKey(1);
        }
        cam.release();
    }
        
    waitKey(0);
    system("pause");
    return 0;
}