opencv报错 error: (-215) size.width>0 && size.height>0 in function cv::imshow

使用opencv读取摄像头并且显示事出现此问题：

后来发现是图像为空时的错误，加入：

  if(!frame.empty())
        imshow("video",frame);

完整的代码：

int main()
{
   /* unsigned char buf_show[1920*1080*3];
    uint32_t addr_bar0;
    unsigned char *bar0_map_base;
    long int screensize = 0;
    unsigned char *fbp = NULL;
    unsigned char *ptail;
    Mat MatRGB ;*/       

    VideoCapture cap();

    if(!cap.isOpened())
    printf("camre open failed!\n");
    Mat frame;
    namedWindow("video");
    if(!frame.empty())
        imshow("video",frame);
    else
        printf("image empty\n");
    )
    {
    cap>>frame;
    if(!frame.empty())
        imshow("video",frame);
    else
        printf("image empty\n");
    )==)
       break;

    }
   cap.release();