opencv3.4 VideoCapture读取视频流保存图片，保存视频和视频合并操作

左手的ㄟ右手 2022-02-22 23:36 270阅读 0赞

简单的学习了VideoCapture类并进行了如下三种应用：

1.  从摄像头读取视频流读取视频帧保存为图片
2.  从摄像头读取视频流读取视频帧保存为视频
3.  多个视频合成一个视频窗口播放  
    具体见代码所示：

/*
    1)从摄像头读取视频流
    2)读取视频帧保存为图片
    3)读取视频帧保存为
    */
    int readFromCamera()
    {
    	VideoCapture capture(0);//0表示打开默认的摄像头，自动探测
    	if (!capture.isOpened())
    	{
    		cout << "open camera failed..\n" << endl;
    		return -1;
    	}
    	//视频流属性
    	//VideoCaptureProperties ------> CV_CAP_PROP_XXX
    	//想要获取视屏对的属性信息，通过get()方法获取
    	double fps = capture.get(CV_CAP_PROP_FPS);//帧信息
    	cout << "每秒" << fps << "帧" << endl;
    
    	int frameWidth = capture.get(CAP_PROP_FRAME_WIDTH);
    	int frameHeight = capture.get(CAP_PROP_FRAME_HEIGHT);
    	cout << frameWidth << "*" << frameHeight << endl;
    
    	/* VideoWriter:
    	 The constructors / functions initialize video writers.
    	- On Linux FFMPEG is used to write videos;
    	-On Windows FFMPEG or VFW is used;
    	-On MacOSX QTKit is used.
    
    	VideoWriter(const String& filename, int fourcc, double fps,
    			Size frameSize, bool isColor = true);
    	*/
    
    	/*
    	http://www.fourcc.org/codecs.php 网页列出相应的编码格式
    	常用的有：
    	CV_FOURCC('P','I','M','1') = MPEG-1 codec
    	CV_FOURCC('M','J','P','G') = motion-jpeg codec
    	CV_FOURCC('M', 'P', '4', '2') = MPEG-4.2 codec
    	CV_FOURCC('D', 'I', 'V', '3') = MPEG-4.3 codec
    	CV_FOURCC('D', 'I', 'V', 'X') = MPEG-4 codec
    	CV_FOURCC('U', '2', '6', '3') = H263 codec
    	CV_FOURCC('I', '2', '6', '3') = H263I codec
    	CV_FOURCC('F', 'L', 'V', '1') = FLV1 codec
    
    	*/
    	//写入的Size()尺寸要和前面读取到的帧尺寸大小相同，否则无法写入视频,大小一直为0KB或者6KB
    	VideoWriter writer("av_1.avi", CV_FOURCC('D', 'I', 'V', 'X'), 25.0, Size(frameWidth, frameHeight), true);//构造函数方式
    	//VideoWriter writer;
    	//writer.open("av_2.avi", CV_FOURCC('D', 'I', 'V', 'X'), 30.0, Size(frameWidth, frameHeight0), true);//调用open函数方式
    
    	Mat frame, bgmask;
    	namedWindow("showVideo", CV_WINDOW_NORMAL);
    	//Ptr<BackgroundSubtractor> pMOG2 = createBackgroundSubtractorMOG2();
    	//pMOG2->apply(frame, bgmask, 0.5);
    	int count = 0;
    	char imagePath[20];
    	while (capture.read(frame))
    	{
    		imshow("showVideo",frame);
    		
    		if (count<100)
    		{
    			sprintf(imagePath, "E://image//img_%03d.jpg", count);
    			imwrite(imagePath,frame);//保存前100帧图像
    			count++;
    		}
    		writer.write(frame);//写入视频文件
    		char a = waitKey(10);//10毫秒内是否退出，27对应键盘的ESC键是否按下
    		if (a == 27)
    		{
    			break;
    		}
    	}
    	writer.release();//释放资源
    	capture.release();//释放资源
    	return 0;
    }

/*
    多个视频合成视频窗口播放
    */
    void mergeVideo()
    {
    	VideoCapture capture1;
    	VideoCapture capture2;
    	capture1.open("av_1_1.avi");
    	capture2.open("av_1_2.avi");
    	if (!capture1.isOpened() && !capture2.isOpened())
    	{
    		cout << "open video1 failed..\n" << endl;
    		return;
    	}
    	Mat frame1, frame2;
    	VideoWriter writer("av_3.avi", CV_FOURCC('D', 'I', 'V', 'X'), 30.0, Size(640,420), true);
    	while (capture1.read(frame1) && capture2.read(frame2))
    	{
    		Mat result(Size(640, 420),CV_8UC3,Scalar::all(0));
    		resize(frame1, frame1, Size(640, 210));
    		resize(frame2, frame2, Size(640, 210));
    		Mat roi1 = result(cv::Rect(0,0,640, 210));
    		Mat roi2 = result(cv::Rect(0, 210,640,210));
    
    		frame1.copyTo(roi1);
    		frame2.copyTo(roi2);
    		imshow("result", result);
    		writer.write(result);
    		char a = waitKey(10);//10毫秒内是否退出，27对应键盘的ESC键是否按下
    		if (a == 27)
    		{
    			break;
    		}
    
    	}
    	capture1.release();
    	capture2.release();
    	writer.release();
    	waitKey(0);
    	
    }

#include <opencv2/highgui/highgui.hpp>
    #include <opencv2/core/core.hpp>
    #include <opencv2/imgproc/imgproc.hpp>
    #include <opencv2/imgcodecs/imgcodecs.hpp>
    //#include <opencv2/video/video.hpp>
    #include <opencv2/videoio/videoio.hpp>
    
    #include <iostream>
    
    using namespace std;
    using namespace cv;
    
    int main()
    {	
    	//readFromCamera();
    	mergeVideo();
    	waitKey(0);
    	return 0;
    
    }