Opencv (C++) notes--open the camera, save the camera video

1--Turn on the camera

Key code statement:

① VideoCapture cam(0);

② cam.read(img);

③ imshow("cam", img);

# include<opencv2/opencv.hpp>
# include<cstdio>
using namespace cv;
using namespace std;

int main(int argc, char *argv[]){
    // 打开摄像头
    VideoCapture cam(0); 
    if (!cam.isOpened()){
        cout << "cam open failed!" << endl;
        getchar();
        return -1;
    }

    cout << "cam open success!" << endl;
    namedWindow("cam");
    Mat img;

    for(;;){
        cam.read(img); // 读帧
        if (img.empty()) break; 
        imshow("cam", img); // 显示每一帧

        if (waitKey(5) == 'q') break; // 键入q停止
    }

    return 0;
}

2--Save camera video

key code:

①VideoWriter vw

②vw.open(): Fourcc specifies the encoding format ( common encoding method ), fps specifies the frame rate, and Size specifies the size

③vw.write()

# include<opencv2/opencv.hpp>
# include<cstdio>
using namespace cv;
using namespace std;

int main(int argc, char *argv[]){
    // 打开摄像头
    VideoCapture cam(0); 
    if (!cam.isOpened()){
        cout << "cam open failed!" << endl;
        getchar();
        return -1;
    }
    cout << "cam open success!" << endl;

    namedWindow("cam");
    Mat img;
    VideoWriter vw;
    int fps = cam.get(CAP_PROP_FPS); // 获取原视频的帧率
    if (fps <= 0) fps = 25;
    
    vw.open("./out1120.avi",
        VideoWriter::fourcc('X', '2', '6', '4'),
        fps,
        Size(cam.get(CAP_PROP_FRAME_WIDTH), 
            cam.get(CAP_PROP_FRAME_HEIGHT))
        );

    if (!vw.isOpened()){ // 判断VideoWriter是否正常打开
        cout << "videoWriter open failed!" << endl;
        getchar();
        return -1;
    }
    cout << "videoWriter open sucess!" << endl;
    for(;;){
        cam.read(img); // 读帧
        if (img.empty()) break; 
        imshow("cam", img); // 展示当前帧
        /* 
        这里可以添加对当前帧的处理操作
        */
        vw.write(img); // 保存当前帧
        if (waitKey(5) == 'q') break; // 键入q停止
    }

    return 0;
}

Note: Executing the above code on Windows may report the following error:

Solution: Download the corresponding version of the library file from the output URL , and place it in the same directory as the executable file .exe, or add the path of the dll file to the system variable path.

 Result: The generated out1120.avi can be played normally;