Video reading

Video reading mainly uses the methods under VideoCapture class to open the video and obtain the frames in the video. The specific examples are as follows:

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

int main()
{
    VideoCapture capture;
    Mat frame;
    frame= capture.open("E:/image/a1.avi");
    if(!capture.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }
    namedWindow("output", CV_WINDOW_AUTOSIZE);

    while (capture.read(frame))
    {
        imshow("output", frame);
        waitKey(10);
    }
    capture.release();
    return 0;
}

When the parameter of capture.open() is 0, it is to read the camera:

frame= capture.open(0);

Video write

Get the video through the camera, and then get the width and height of the current frame through capture.get (CV cap Pro frame width), and create a VideoWriter class object writer to write the video.
Simple video processing can be performed before writing.

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

int main()
{
    VideoCapture capture;
    capture.open(0);
    if(!capture.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }

    Size size = Size(capture.get(CV_CAP_PROP_FRAME_WIDTH), capture.get(CV_CAP_PROP_FRAME_HEIGHT));
    VideoWriter writer;
    writer.open("E:/image/a2.avi", CV_FOURCC('M', 'J', 'P', 'G'), 10, size, true);

    Mat frame, gray;
    namedWindow("output", CV_WINDOW_AUTOSIZE);

    while (capture.read(frame))
    {
        //Convert to black and white image
        cvtColor(frame, gray, COLOR_BGR2GRAY);  
        //Binary treatment 
        threshold(gray, gray, 0, 255, THRESH_BINARY | THRESH_OTSU);
        cvtColor(gray, gray, COLOR_GRAY2BGR);
        imshow("output", gray);
        writer.write(gray);
        waitKey(10);
    }

    waitKey(0);
    capture.release();
    return 0;
}