undistortFisheyeImage function How does it work?

How does this function work? According to the documentation, I understand the general process, but I don't know how to convert the distortion image to undistort image step by step, that is, what is the corresponding mapping step? I appreciate your answer.

https://www.mathworks.com/help/vision/ref/undistortfisheyeimage.html

Answer 1

[cui,xingxing]

Refer to Scaramuzza fisheye model implemention