title: How to put CGContextScaleCTM and CGContextTranslateCTM outside of drawRect?
body: <p>I am rather beginner at this kind of path drawing, but when displaying a map, I realised that CGContextScaleCTM and CGContextTranslateCTM take up a lot of time inside my drawRect.
  That would be good to bring those outside. Since I always draw the same map, I think that should be possible. But how?</p>