Get size of UIView after applying CGAffineTransform

Question

I was surprised not to find an answer to this question, maybe is something very simple I somehow overlook :

How to get the real size of an UIView after I apply a CG

Answer 1

Simpler: A view with (bounds) size s to which transform tr is applied has resulting size:

CGSizeMake(s.width*hypotf(tr.a, tr.b), s.height*hypotf(tr.c, tr.d))

However, if view's superview or any ancestor view has any non-unit transform applied, this size makes little sense in absolute terms.

If you want the absolute size of a view in window coordinates after any arbitrary transform has been applied to that view or its superviews, you should first compute the absolute transform matrix by composing all the view transform up to the root window, and then apply the above formula to the result.