The only way I know of to transfer an image is to tranfer it onto special paper such as this click here for going onto glass or this click here for sticking on things. You do get waterslide transfers but I don't know who does them but its probably not edible so isn't really suitable and I'm fairly sure the ink from your printer is toxic.
You don't want to make a cake that will make they sick do you?
Someone might well know how they do it, its obviously a special type of paper they use but I'm fairly sure it must be a special printer, as I said I'm fairly sure normal printer ink is toxic, could be wrong but I think it is.
How about making a puzzle or a mousepad instead click here no chance of poisoning someone that way.
Incidently could you please next time you post choose a better title than Help! Something like how do you print on a cake would have been better than Help!
Good luck hope someone gives you the info you want.