Kronephon - 1 month ago 5

C++ Question

I'm running into an issue with c++. My idea is to fill an intrinsic matrix with predefined values for camera calibration, except I don't seem to be doing it properly.

`Mat intrinsic_Matrix(3,3, CV_64F);`

float fx = (4032 * 4)/6.69; //2410.76

float fy = (3024 * 4)/5.55; //2179.45

float cx = 2016.0;

float cy = 1512.0;

cout << intrinsic_Matrix << endl;

cout << endl;

intrinsic_Matrix.at<float>(0,0) = fx;

intrinsic_Matrix.at<float>(0,1) = 0.0;

intrinsic_Matrix.at<float>(0,2) = cx;

intrinsic_Matrix.at<float>(1,0) = 0.0;

intrinsic_Matrix.at<float>(1,1) = fy;

intrinsic_Matrix.at<float>(1,2) = cy;

intrinsic_Matrix.at<float>(2,0) = 0.0;

intrinsic_Matrix.at<float>(2,1) = 0.0;

intrinsic_Matrix.at<float>(2,2) = 1.0;

cout << intrinsic_Matrix << endl;

calibrateCamera(frameWorldPoints, bothImagePoints, cvSize(referimages[0].image.cols, referimages[0].image.rows), intrinsic_Matrix, distortion_coeffs, rvecs, tvecs, CV_CALIB_USE_INTRINSIC_GUESS);

The output on both prints makes little sense. Looks like I'm looking at pointer values or uninitialized values. Also, opencv throws a "intrinsic matrix not correct" exception when I try to calibrate it so I'm sure it's not that I'm printing it wrong.

Answer

You initialize MAT with 64F but use floats. Either change to 32F as follows

```
Mat intrinsic_Matrix(3,3, CV_32F);
float fx = (4032 * 4)/6.69; //2410.76
float fy = (3024 * 4)/5.55; //2179.45
float cx = 2016.0;
float cy = 1512.0;
cout << intrinsic_Matrix << endl;
cout << endl;
intrinsic_Matrix.at<float>(0,0) = fx;
intrinsic_Matrix.at<float>(0,1) = 0.0;
intrinsic_Matrix.at<float>(0,2) = cx;
intrinsic_Matrix.at<float>(1,0) = 0.0;
intrinsic_Matrix.at<float>(1,1) = fy;
intrinsic_Matrix.at<float>(1,2) = cy;
intrinsic_Matrix.at<float>(2,0) = 0.0;
intrinsic_Matrix.at<float>(2,1) = 0.0;
intrinsic_Matrix.at<float>(2,2) = 1.0;
cout << intrinsic_Matrix << endl;
calibrateCamera(frameWorldPoints, bothImagePoints, cvSize(referimages[0].image.cols, referimages[0].image.rows), intrinsic_Matrix, distortion_coeffs, rvecs, tvecs, CV_CALIB_USE_INTRINSIC_GUESS);
```

or

change all your variables to double, keeping intrinsic_matrix initialized as 64F

```
Mat intrinsic_Matrix(3,3, CV_64F);
double fx = (4032 * 4)/6.69; //2410.76
double fy = (3024 * 4)/5.55; //2179.45
double cx = 2016.0;
double cy = 1512.0;
cout << intrinsic_Matrix << endl;
cout << endl;
intrinsic_Matrix.at<double>(0,0) = fx;
intrinsic_Matrix.at<double>(0,1) = 0.0;
intrinsic_Matrix.at<double>(0,2) = cx;
intrinsic_Matrix.at<double>(1,0) = 0.0;
intrinsic_Matrix.at<double>(1,1) = fy;
intrinsic_Matrix.at<double>(1,2) = cy;
intrinsic_Matrix.at<double>(2,0) = 0.0;
intrinsic_Matrix.at<double>(2,1) = 0.0;
intrinsic_Matrix.at<double>(2,2) = 1.0;
cout << intrinsic_Matrix << endl;
```

Source (Stackoverflow)

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