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 CGAffineTransform to it?

eg.

my UIView has size 300 x 200, I apply a scaling transform let's say factor 2 both horizontal and vertical, so the UIView now takes 600 x 400 on the screen, but it's bounds and it's layer's bounds are still returning a size of 300 x 200 ... where do I find the real size of the UIView ?

ps. forgot to mention I want to also rotate the uiview. If I apply only scaling CGSizeApplyAffineTransform works great, but when there's also rotation, then it does not work properly.

Edit: drawnonward pointed me in the right direction, I just refined a bit the code to compile and here it is :

UIView* view = (your view being transformed);
CGAffineTransform trans = (view.transform or create a new transformation);

CGRect rect = [view bounds];
CGMutablePathRef path = CGPathCreateMutable();
rect.origin = CGPointZero;
CGPathAddRect(path , &trans , rect);
rect = CGPathGetBoundingBox( path );
CGPathRelease( path );

Now rect.size contains the dimensions of the view with the transformation applied Thanks again to drawnonward

Answer 1

I use this in Objective C:

CGRect transformedBounds = CGRectApplyAffineTransform(view.bounds, view.transform);

or in Swift 4:

let transformedBounds = view.bounds.applying(view.transform)

Answer 2

[myView frame] returns the frame of the view as seen by the parent, for layout and relative sizes. [myView bounds] returns the bounds of the view as seen by itself, for drawing. If you have transforms applied to multiple views, you can use convertRect: to or from a view.

Edit:

Maybe something like this.

CGRect rect = [view bounds];
CGPathRef path = CGPathCreateMutable();
rect.origin = CGPointZero;
CGPathAddRect( rect , [view transform] );
rect = CGPathGetBoundingBox( path );
CGPathRelease( path );

The use [view center] to find the position in the superview.

Answer 3

Old question, but bumped into here, after searching a solution and tons of attempts. It was simple;

view.layer.frame has all transformations applied and you'll get the size from view.layer.frame.size easily.

-- below here is not an answer to this question - -

And for my problem, I was trying to calculate new center value after changing layer.anchorPoint of my rotated view, so it doesn't move. And finally did it like this;

CGPoint topLeft = [self.superview convertPoint:CGPointMake(0, 0) fromView:self];
self.layer.anchorPoint = CGPointMake(0, 0);
self.center = topLeft;

for reverse

CGPoint center = [self.superview convertPoint:CGPointMake(self.bounds.size.width / 2, self.bounds.size.height / 2) fromView:self];
self.layer.anchorPoint = CGPointMake(.5, .5);
self.center = center;

finally.