As per OpenCV, the KANNALA_BRANDT mode has the camera parameters named
fx, fy, cx, cy, and distortion parameters as k1, k2, k3 and k4
However, as mentioned in the code in this repo
https://github.com/hengli/camodocal/blob/7211aaf6869c94e5de4696c93ece8ade975a3e56/src/camera_models/EquidistantCamera.cc#L17-29
I understand that mu and mv are fx and fy respectively
Similarly, u0 and v0 are cx and cy respectively.
How about the distortion coefficients? Where is the parameter k1?