How to add an ID to an image in CKEditor?

Everytime a user inserts an image into the page (I'm using CKEditor 4 inline editing) I want to add an ID sequentially e.g. id=Image1, id=Image2, id=Image3 so that my server can loop through them and know how many images there are on the page and how to process them.

I noticed there is an addClass() function in CKEditor, but how do I add an ID? I just need some way to uniquely and programmatically tell each inserted image apart from the other.

I can't understand how to do this at all. Even a pointer in the right direction would be very appreciated.