How should one get a waiter's attention?

Here’s the scenario; My friend and I were in a restaurant for lunch. We had finished our meals and were talking and my friend wanted someone to take a picture of us. He waved his hand – I didn’t quite see it – at a waiter who was some feet away. He did not snap his fingers or shout, “Garcon.” The waiter came and took our picture but as he walked away, he said, “Just for future reference you should not do that to summon a waiter.’ I’m wondering if that does seem rude to others and if so, what one should do.

Not agonizing, just curious for some reactions.