IANAL but if I'm going to shove food in my mouth and digest it, at some point that food belongs to me. Now you can argue that it only becomes mine at the moment the bill is paid, but I can argue it's mine the moment it's set on my table. Otherwise you could have "authors" reaching down my throat into my stomach to retrieve their "work" if they suddenly decide their "work" was too precious to sell to me or they want to renege on the deal. The fact that payment is given after the meal doesn't change the fact that the meal is mine the moment it's on the table. So if I take a picture of it on the table, I'm taking a picture of my stuff which I purchased.
Or are we going to start arguing that restaurants "license" their food?
"The fundamental principle of science, the definition almost, is this: the sole test of the validity of any idea is experiment." -- Richard P. Feynman