Opencv：cvGetMat中的空指针（传递NULL数组指针） [英] Opencv: Null pointer (NULL array pointer is passed) in cvGetMat

问题描述

我尝试使用opencv从网络摄像头捕获视频时收到此错误。这是我使用的代码：

I'm getting this error when trying to capture video from webcam using opencv. This is the code I'm using:

#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）：

The error occur at cvShowImage("text", frame):

OpenCV错误：cvGetMat，
文件中的NULL指针（传递NULL数组指针）
/ 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调用抛出异常
（lldb ）

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)

它是什么错误，如何解决呢？

What is it error about and how can I fix it?

推荐答案

首先，您应该检查在索引0是否有设备，例如

First you should check that whether there is a device at index 0, like this

  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
}

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