视频读取

视频读取，主要利用VideoCapture类下的方法打开视频并获取视频中的帧，具体示例如下：

#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;
}

capture.open()的参数为0时为读取摄像头：

frame= capture.open(0);

视频写入

通过摄像头获取视频，然后通过capture.get(CV_CAP_PROP_FRAME_WIDTH), capture.get(CV_CAP_PROP_FRAME_HEIGHT)获取当前帧的宽度和高度，创建一个VideoWriter类对象writer进行视频的写入。
写入前可进行视频的简单处理。

#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))
    {
        //转换为黑白图像
        cvtColor(frame, gray, COLOR_BGR2GRAY);  
        //二值化处理 
        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;
}