How to manage UIImageView content mode?

Please try this code, Hope it will work for you.

set UIImageView contentMode to UIViewContentModeScaleAspectFill as below :

imageView.contentMode = UIViewContentModeScaleAspectFill;

set autoresizingMask of UIImageView as below :

imageView.autoresizingMask =   
    ( UIViewAutoresizingFlexibleBottomMargin
    | UIViewAutoresizingFlexibleHeight
    | UIViewAutoresizingFlexibleLeftMargin
    | UIViewAutoresizingFlexibleRightMargin
    | UIViewAutoresizingFlexibleTopMargin
    | UIViewAutoresizingFlexibleWidth );