opencv - How to calculate radius in orb?

Question

Studying ORB feature descriptors from it is the official paper I found it stating:

We empirically choose r to be the patch size, so that that x and y run from [−r, r]. As |C| approaches 0,

I did not understand how r is calculated, please tell me how to calculate r.

I tried a lot to dig deeper using the internet but I couldn't find formula or explaining and I did not understand what it stated means.

Would you please explain it for me? And give me the formula if you may.

Answer 1

论文说：

“我们凭经验选择r作为补丁大小，......”

在 OpenCV 中，使用了 31 的补丁大小（似乎是标准值）。
具有指定大小的强度块用于描述 FAST 关键点。由于ORB 使用BRIEF 描述符，因此图像补丁被传输到二进制字符串中，该字符串稍后会进行比较以匹配关键点。更多细节可在 简要论文中找到。因此，如果您增加 r，您将增加二进制字符串的大小。因此半径不是通过某些公式计算的，而是由开发人员/用户选择的。