Version of Ceres

[zhuangaoooo]

In the README.md of the project, the version of Ceres isn't specified, and the download link for Ceres will guide you to download Ceres 2.2.0. However, there may be some errors when using 'make' with Ceres 2.2.0 (part of the error is shown at the end of this issue, there may be some errors with 'new ceres::QuaternionParameterization()' in Ceres 2.2.0). I found that such errors will not occur if I use Ceres 2.0.0.

So I suggest specifying that the version of Ceres should be 2.0.0 in the README.md.

/textslam/TextSLAM/src/optimizer.cc:653:48: error: expected type-specifier
653 | problem.AddParameterBlock(Sim3Pose, 4, new ceres::QuaternionParameterization());
| ^~~~~

[bupt-yfh]

Thanks for the comment! I have the same problem. My ubuntu system is 18.04. And when I use ceres 2.0.0, the error not occur!