How to non-deforming rotate an image in UIImageView in UIView when device rotates?

Question

Hi everybody, I have a UIView with this structure inside it:

UIView
-- UIImageView
-- -- UIImage

The JPG image is vertical, and it's the same size of the device in the vertical orientation.
I want the UIImage to rotate this as follow:

Device is vertical:
The image is shown full size (fills the screen)

Device is horizontal:
- The image width should match the device width in horizontal orientation
- The image height should be calculated to NOT DEFORM the image (so its bottom part will be out of the UIImageView)

I'm going crazy trying to solve this.
Anybody have already solved this problem?

Thank you in advance.