Camera Calibration in Java OpenCv

Question

I have been struggling to calibrate my camera in Java, the parameters that I receive from calling

Calib3d.calibrateCamera(object_points, corners, gray.size(), cameraMatrix, distCoeffs, rvecs, tvecs);

are way off.

If I use the same image in Python (tutorial) the results are correct . I really don't know how to fix this problem.I really see no difference.(Maybe the way I am initializing object_points?)

Here is the java code

found_chess = Calib3d.findChessboardCorners(gray, patternSize, actual_corners,  Calib3d.CALIB_CB_ADAPTIVE_THRESH + Calib3d.CALIB_CB_NORMALIZE_IMAGE);
if(found_chess)
{

    corners.add(actual_corners);
    //cornersubPix() irrelevant since all the corners are found in findChessBoard
    //Imgproc.cornerSubPix(gray, actual_corners, new Size(SIZE_Y*2+1,SIZE_X*2+1), new Size(-1,-1), new TermCriteria(TermCriteria.EPS+TermCriteria.MAX_ITER,30,0.1));

    MatOfPoint3f points;

    Mat a = new MatOfPoint3f();
        for(int y=0; y<SIZE_Y; ++y) 
        {
            for(int x=0; x<SIZE_X; ++x)
            {
                points = new MatOfPoint3f(new Point3(x, y, 0));
                a.push_back(points);
            }
        }

    object_points.add(a);
    Calib3d.calibrateCamera(object_points, corners, gray.size(), cameraMatrix, distCoeffs, rvecs, tvecs);
 }

The Python code that I use can be found in here

I am only using one image, but shouldn't be the parameters the same. The chess_corners found are exactly the same.

Here are the parameters that I am getting in java(which are non-sense)

K1: 519.399710654873
K2: -42465.04562762376
P1: -11.363668181023353
P2: -1.5606689962722413
K3: -661829.1347551622
Fx: 8848.871073244098
Cx: 850.1589437229045
Fy: 9242.065368089003
Cy: 471.258611493399

I would really apreciate if someone could help me out . Thank you in advance

Ignacio Ferrero · Accepted Answer · 2014-08-31 11:59:50Z

1

It seems I was initializing objectpoints the wrong way. Changed X and Y and it works fine(See code and results)

for(int x=0; x<SIZE_X; ++x) 
{
    for(int y=0;  y<SIZE_Y; ++y)
    {
        points = new MatOfPoint3f(new Point3(y, x, 0));
        a.push_back(points);
    }
}

K1: -0.018826429817406057
K2: 0.004765861493124195
P1: -0.013705374382823956
P2: 0.004067969604879225
K3: -0.05266506928016909
Fx: 594.0637743671965
Cx: 657.3929211728023
Fy: 604.1989278105854
Cy: 572.8441406065865

answered Aug 31, 2014 at 11:59

Ignacio Ferrero

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