opencv学习笔记之获取摄像头的视频帧

介绍

• 获取PC连接的摄像头下的视频流，个性化设置拍摄时的参数和按键等

• 用于拍摄获取特定场景下的视频

• windows代码如下：

#include <iostream>
#include <time.h>
#include <opencv2/opencv.hpp>

#ifdef _WIN32
#include <Windows.h>
#include <io.h>
#include <direct.h>
#else
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>
#endif

/****************
// timeStamp convert to stardard time format
*******/
void getStdTimeFormat(time_t nTimeStamp, char* pStdTimeFormat)
{
    char pTmpString[128] = { '\0' };
#ifdef _WIN32
    struct tm pTmStruct;
    localtime_s(&pTmStruct, &nTimeStamp);
    sprintf_s(pTmpString, sizeof(pTmpString), "%04d_%02d_%02d-%02d_%02d_%02d", pTmStruct.tm_year + 1900, pTmStruct.tm_mon + 1, pTmStruct.tm_mday, \
		pTmStruct.tm_hour, pTmStruct.tm_min, pTmStruct.tm_sec);
    memcpy(pStdTimeFormat, pTmpString, strlen(pTmpString));
#else
    tm *pTmStruct = localtime(&nTimeStamp);
	sprintf(pTmpString, "%04d-%02d-%02d %02d:%02d:%02d", pTmStruct->tm_year + 1900, pTmStruct->tm_mon + 1, pTmStruct->tm_mday, \
		pTmStruct->tm_hour, pTmStruct->tm_min, pTmStruct->tm_sec);
	//strcpy(pStdTimeFormat, pTmpString);
	memcpy(pStdTimeFormat, pTmpString, strlen(pTmpString));
#endif // _WIN32

    //timeStream = std::string(pTmpString);
    return;
}
using namespace std;

int main(int argc, char** argv){
    int frame_width = 640;
    int frame_height = 480;

    double fps = 25.0;// framerate of the created video stream
    if(argc == 2){
        printf("Usage: ./Demo.exe fps\n");
        int fps_value = atoi(argv[1]);
        fps = 1.0f*fps_value;
    }
    if(argc == 3){
        printf("Usage: Demo.exe  FrameWidth FrameHeight\n");
        frame_width = atoi(argv[1]);
        frame_height = atoi(argv[2]);
    }
    if(argc == 4){
        printf("Usage: Demo.exe  fps FrameWidth FrameHeight\n");
        int fps_value = atoi(argv[1]);
        fps = 1.0f*fps_value;
        frame_width = atoi(argv[2]);
        frame_height = atoi(argv[3]);
    }
    if(argc >4){
        printf("Usage: Demo.exe  fps FrameWidth FrameHeight\n");
        return -1;
    }
	cv::Mat src;
	// use default camera as video source
	cv::VideoCapture cap(0);
	// check if we succeeded
	if (!cap.isOpened()) {
		std::cerr << "ERROR! Unable to open camera\n";
		return -1;
	}
    cap.set(cv::CAP_PROP_FRAME_WIDTH, frame_width);
    cap.set(cv::CAP_PROP_FRAME_HEIGHT,frame_height);

    cout << "Frame width: " << cap.get(cv::CAP_PROP_FRAME_WIDTH) << endl;
    cout << "Frame height: " << cap.get(cv::CAP_PROP_FRAME_HEIGHT) << endl;

	// get one frame from camera to know frame size and type
	cap >> src;
	// check if we succeeded
	if (src.empty()) {
		cerr << "ERROR! blank frame grabbed\n";
		return -1;
	}

    bool isColor = (src.type() == CV_8UC3);
	//--- INITIALIZE VIDEOWRITER
	cv::VideoWriter writer;
	int codec = cv::VideoWriter::fourcc('M', 'J', 'P', 'G');  // select desired codec (must be available at runtime)

	time_t nTimeStamp = time(NULL);
    char pStdTimeFormat[64]={0x0};
    getStdTimeFormat(nTimeStamp, pStdTimeFormat);

#ifdef _WIN32
    const char* cmdpath = _getcwd(NULL, 0);

    char saveDir[256] = {0x0};
    sprintf_s(saveDir, 255, "%s\\Frames_%s\\", cmdpath, pStdTimeFormat);

    if(0 != _access(saveDir,0))
    {
        _mkdir(saveDir);//create the folder
        //printf("dest folder had created. \n");
    }
#else
    const char* cmdpath = get_current_dir_name();
    char saveDir[256] = {0x0};
    sprintf(saveDir, "%s/Frames_%s/", cmdpath, pStdTimeFormat);

    if ( 0 != access(saveDir.c_str(),0))//if this is not a directory
    {
        mkdir(saveDir.c_str(),0755);//create the folder
        //printf("dest folder had created. \n");
    }
#endif

    char tmpfilename[256] = {0x0};
    sprintf(tmpfilename,"./video_%s.avi", pStdTimeFormat); // name of the output video file

    std::string filename(tmpfilename);
    writer.open(filename, codec, fps, cv::Size(cap.get(cv::CAP_PROP_FRAME_WIDTH),    cap.get(cv::CAP_PROP_FRAME_HEIGHT)), isColor);

    // check if we succeeded
	if (!writer.isOpened()) {
		cerr << "Could not open the output video file for write\n";
		return -1;
	}
    size_t nFrames = 0;
    size_t index = 0;
    bool enableQuit = false;

    cv::namedWindow("capture frame", cv::WINDOW_NORMAL | cv::WINDOW_FULLSCREEN);
    for (;;)
    {
        // check if we succeeded
        if (!cap.read(src)) {
            cerr << "ERROR! blank frame grabbed\n";
            break;

        }
        nFrames++;
        // encode the frame into the video file stream
        writer.write(src);
        // show live and wait for a key with timeout long enough to show images
        cv::imshow("capture frame", src);
        int key = cv::waitKey(5);
        switch (key) {
            case 32: // Spacebar to save a frame mat
            {
                index++;
                char saveString[256];
                sprintf(saveString,"%s%05zd.png",saveDir, index);
                cv::imwrite(saveString, src);
                break;
            }
            case 27: //ESC to quit
            {
                enableQuit = true;
                break;
            }
            default:
                continue;
        }
        if(enableQuit){
            break;
        }
    }
    cv::destroyAllWindows();
	// the video file will be closed and released automatically in VideoWriter destructor
	return 0;
}