Json Config help


I’m trying to add new custom model i’ve trained with keras (.h5) and I cannot figure out what should I put in json config by the following parameters (mean and std):

"mean":0.5, // ??
"std":255, // ??

I found this, but it didn’t tell me much :\

std The input image is divided by this value, (Standard Deviation)
mean This is subtracted from the image after dividing by the std