c++ - Opencv:cvGetMat 中的空指针(传递空数组指针)

Question

尝试使用 opencv 从网络摄像头捕获视频时出现此错误。这是我正在使用的代码:

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

int main( int argc, const char** argv ) {
    CvCapture *capture = cvCaptureFromCAM(0);
    IplImage *frame;
    cvNamedWindow("test");

    while ( 1)
    {
        frame = cvQueryFrame(capture) ;
        cvShowImage("test",  frame);
        int key = cvWaitKey(1);
        if ( key == 27 ) break;   // ESC key was pressed
    }

    // Memory deallocation
    cvReleaseCapture(&capture);
    cvDestroyWindow("test");

    return 0;
}

错误发生在 cvShowImage("text", frame):

OpenCV Error: Null pointer (NULL array pointer is passed) in cvGetMat, file /opt/local/var/macports/build/_opt_mports_dports_graphics_opencv/opencv/work/opencv-2.4.6.1/modules/core/src/array.cpp, line 2382 libc++abi.dylib: terminate called throwing an exception (lldb)

这是什么错误，我该如何解决？

Answer 1

首先你应该检查索引0处是否有设备，像这样

  if (!capture)
  {
      // print error and exit
      cout << "ERROR: Capture is null!\n";
      return -1;
  }

其次:

while ( capture)
{
     frame = cvQueryFrame(capture) ;
     cvShowImage("test",  frame);
     int key = cvWaitKey(1);
     if ( key == 27 ) break;   // ESC key was pressed
}

希望对你有帮助