SFML sprite rotation

[Disch]

Does sfml have a sprite.getSize() maybe?

It does.

It's all in the docs. For simple things like this, you should really check the docs page first, as it should be very easy to spot your answer (that way you don't have to wait for someone to respond to the forum post).

Specifically, since you have an sf::Sprite, check the sf::Sprite page:
http://sfml-dev.org/documentation/1.6/classsf_1_1Sprite.php

You'll notice that it does in fact have a GetSize function:
http://sfml-dev.org/documentation/1.6/classsf_1_1Sprite.php#a386e09c5f321a69707393851ae026f7e