Hi,
So actually, I found that image path is generated right when I drop or select an image in the image field, so before I save the product.
Tell me if I'm wrong but I think this part is manage in a js file ?
So if I really understand, the path is generate from a sort of id which depends on the last one registered.
I learnt a lot of things but i think it's too far from what I'm searching for at the beginning explained in that post :
Thanks a lot for your help.