原理就是根据数据构建求解方程组，分析其系数矩阵的性质进行求解。

1 案例演示

Eigen::Vector2d ellipseFitting2D(const PCLPointCloud::Ptr points)
{Eigen::Matrix<double, Eigen::Dynamic, 3, Eigen::RowMajor> D1(points->points.size(), 3);Eigen::Matrix<double, Eigen::Dynamic, 3, Eigen::RowMajor> D2(points->points.size(), 3);for (size_t i = 0; i < points->points.size(); ++i){double x = points->points[i].x;double y = points->points[i].y;D1.row(i) << x * x, x * y, y * y;D2.row(i) << x, y, 1;}Eigen::Matrix<double, 3, 3, Eigen::RowMajor> S1, S2, S3;S1 = D1.transpose() * D1;  // 3*3S2 = D1.transpose() * D2;  // 3*3S3 = D2.transpose() * D2;  // 3*3Eigen::Matrix<double, 3, 3, Eigen::RowMajor> T, M1, M2;T = -S3.inverse() * S2.transpose();M1 = S1 + S2 * T;M2.row(0) = M1.row(2) / 2.0;M2.row(1) = -M1.row(1);M