What causes “OpenCV(4.0.1) Error : Assertion failed(m.dims <= 2)”

Question

What causes this error?

OpenCV: terminate handler is called!The last OpenCV error is : OpenCV(4.0.1) Error : Assertion failed(m.dims <= 2) in cv::F

Answer 1

This error is on this line:

cout << obj << endl;

OpenCV, will only try to output 2D images (maybe 3D is too hard if it has more than 1 channel).

A possible workaround is:

  int ordo[3] = { 2, 2, 2 };
  cv::Mat obj(2, 2, CV_8UC2, cv::Scalar::all(0));
  std::cout << obj << std::endl;

Which is allowed and prints:

[  0,   0,   0,   0;
   0,   0,   0,   0]

First 2 numbers is the first "pixel". You can easily access the x,y,z coordinate doing something like:

// obj.at<cv::Vec2b>(y, x)[z] = uchar value
obj.at<cv::Vec2b>(1, 0)[0] = 255;

Which will print out:

[  0,   0,   0,   0;
 255,   0,   0,   0]

Another possibility is to create a self made printing function which takes the matrix and draws it.