使用openCV从网络摄像头捕获图像的功能仅在首次调用时有效

Question

嗨，我是OpenCV的新手，实际上是一般的编程人员。 我正在尝试编写一个函数，每次调用它时都会从相机捕获单个图像。 我编写了此函数，但仅在第一次调用时才起作用。 我有点跳了起来，但是现在我迷上了，必须解决这个问题。

int main(int argc, char * argv[])
{
    int faceCnt = 1;
    faceCnt = captureFace(faceCnt);
    cout << faceCnt << endl;
    if(faceCnt == -1)
             cout << "A problem has occured << endl;
    faceCnt = captureFace(faceCnt);
    cout << faceCnt << endl;
    if(faceCnt == -1)
             cout << "A problem has occured << endl;
    return 0;
}
int captureFace(int cnt){
    Mat temp;
    VideoCapture cap(0);
    if(!cap.isOpened())  //Check to see if capture was successful
            return -1;
    cap >> temp;
    cap.release();
    char numstr[21]; // enough to hold all numbers up to 64-bits
    sprintf(numstr, "%d", cnt);
    string location = "faces/sub";
    string fileType = ".jpg";
    string result = location + numstr + fileType;
    imwrite(result, temp);
    cout << result << endl;
    cnt++;
    if(cap.isOpened())
       return -1;
    return cnt;
}

从控制台输出：

HIGHGUI ERROR: V4L/V4L2: VIDIOC_S_CROP
Corrupt JPEG data: 1 extraneous bytes before marker 0xd2
faces/sub1.jpg
2HIGHGUI ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV
VIDIOC_STREAMON: Bad file descriptor
Unable to stop the stream.: Bad file descriptor

faces/sub2.jpg
3

查看我得到的错误的其他答案，我发现它们实际上并不重要（尽管我不知道我是否相信）。 我正在为相机使用Logitech C270，并且正在运行xubuntu 13.10。

非常感谢你的帮助！

Answer 1

我注意到关闭和打开同一摄像头的VideoCaptures有时会失败。 最好一次打开网络摄像头并重新使用它。

另外，您不一定需要调用release（），该释放是在VideoCapture的析构函数中自动完成的，或者在再次调用open（）时自动完成的。

int main(int argc, char * argv[])
{
    int faceCnt = 1;
    VideoCapture cap(0);
    faceCnt = captureFace(faceCnt, cap);
    cout << faceCnt << endl;
    if(faceCnt == -1)
             cout << "A problem has occured << endl;
    faceCnt = captureFace(faceCnt, cap);
    cout << faceCnt << endl;
    if(faceCnt == -1)
             cout << "A problem has occured << endl;
    return 0;
}

int captureFace(int cnt, VideoCapture& cap){
    Mat temp;
    if(!cap.isOpened())  //Check to see if capture was successful
            return -1;
    cap >> temp;
    char numstr[21]; // enough to hold all numbers up to 64-bits
    sprintf(numstr, "%d", cnt);
    string location = "faces/sub";
    string fileType = ".jpg";
    string result = location + numstr + fileType;
    imwrite(result, temp);
    cout << result << endl;
    cnt++;
    return cnt;
}