OpenCvSharp.OpenCVException: 'fabs(sc) > DBL_EPSILON'

[wanless79]

Summary of your issue

When running the Cv2.CalibrateCamera function I get this errror OpenCvSharp.OpenCVException: 'fabs(sc) > DBL_EPSILON'

What did you do when you faced the problem?

I checked the obj_points, img_points arrays and both contain the same number of items obj_points has x,y,z values all 0 and img_points has x,y values all with numeric values

I removed all my calib images and replaced them with a single flat checkerboard image, I also attempted to pass in an all 0 obj_points and img_points and still got the same error.

Example code:

           DirectoryInfo dir = new DirectoryInfo("CalibImages");
            var calibFiles = dir.GetFiles().Where(m => m.Extension == ".jpg");

            TermCriteria criteria = new TermCriteria(CriteriaTypes.MaxIter | CriteriaTypes.Eps, 30, 0.001);
            var size = new OpenCvSharp.Size(0, 0);

            int PAT_COL = 10;
            int PAT_ROW = 7;
            int PAT_SIZE = PAT_ROW * PAT_COL;
            OpenCvSharp.Size PatternSize = new OpenCvSharp.Size(PAT_COL, PAT_ROW);

            List<List<Point3f>> obj_points = new List<List<Point3f>>();
            List<List<Point2f>> img_points = new List<List<Point2f>>();
            var objp = np.zeros((PAT_SIZE, 3), np.float32);
            var objpl = NDArrayToList(objp);

            foreach (FileInfo file in calibFiles)
            {
                Mat img = Cv2.ImRead(file.FullName);
                var gray = img.CvtColor(ColorConversionCodes.BGR2GRAY);
                size = img.Size();
                Point2f[] corners;
                var found = Cv2.FindChessboardCorners(gray, PatternSize, out corners);
                if (found)
                {
                    obj_points.Add(objpl);
                    var corners2 = Cv2.CornerSubPix(gray, corners, new OpenCvSharp.Size(6, 6),
                                                new OpenCvSharp.Size(-1, -1), criteria);
                    if (corners2?.Length > 0)
                    {
                        img_points.Add(corners2.ToList());
                    }
                    else
                    {
                        img_points.Add(corners.ToList());
                    }

                }
                gray.Dispose();
                img.Dispose();
            }


            double[,] cameraMatrix = new double[3, 3];
            double[] distCoeffs = new double[5];

            Vec3d[] rvecs = new Vec3d[] { };
            Vec3d[] tvecs = new Vec3d[] { };

            var ret = Cv2.CalibrateCamera(obj_points, img_points, size,
                        cameraMatrix, distCoeffs, out rvecs, out tvecs);

Output:

OpenCvSharp.OpenCVException: 'fabs(sc) > DBL_EPSILON'

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