iOS 11 UIBarButtonItem images not sizing

BarButtonItem (iOS11\xCode9) uses autolayout instead of frames. Try this (Swift):

if #available(iOS 9.0, *) {
    cButton.widthAnchor.constraint(equalToConstant: customViewButton.width).isActive = true
    cButton.heightAnchor.constraint(equalToConstant: customViewButton.height).isActive = true
}

Objective C

if (@available(iOS 9, *)) {
     [cButton.widthAnchor constraintEqualToConstant: standardButtonSize.width].active = YES;
     [cButton.heightAnchor constraintEqualToConstant: standardButtonSize.height].active = YES;
}