Ren´Py image prediction/processing with large transparent areas

[gamedriver]

I think I read somewhere in the manual that Ren´Py crops all image areas without information before processing (but can´t find it right now, sorry). That sounds good, because for me it would be very convenient to work with big image formats for sprites, which contain only about 10 - 20% content. The rest is just empty - this makes it easier for zooming, rotating etc.

But I am somewhat worried to slow down the game because of this. Up to now I can´t see lag, but it would be very reassuring to get this confirmed by more competent experts.

Thanks!!