iOS - Dynamically load navigation bar title image with interpolation. How to use: Set navigation title as "{image_name_here}"

NavigationController.m

#define NAV_PORTRAIT_HEIGHT     44

- (void)viewDidLoad {
    [super viewDidLoad];
    [self loadNavigationBarTitleImage];
}

- (void)loadNavigationBarTitleImage {
    NSString *title = self.navigationItem.title;
    NSInteger prefixLength = NAV_TITLE_IMAGE_PREFIX.length;
    NSInteger suffixLength = NAV_TITLE_IMAGE_SUFFIX.length;
    if (title.length > prefixLength + suffixLength && [title hasPrefix:NAV_TITLE_IMAGE_PREFIX] && [title hasSuffix:NAV_TITLE_IMAGE_SUFFIX]) {
        NSString *imageName = [title substringWithRange:NSMakeRange(prefixLength, title.length-prefixLength-suffixLength)];
        UIImage *image = [UIImage imageNamed:imageName];
        if (image) {
            UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
            imageView.contentMode = UIViewContentModeScaleAspectFit;
            imageView.autoresizingMask = UIViewAutoresizingFlexibleHeight;
            CGRect imageFrame = imageView.frame;
            imageFrame.size.height = self.navigationController.navigationBar.bounds.size.height * (imageFrame.size.height / NAV_PORTRAIT_HEIGHT);
            imageView.frame = imageFrame;
            self.navigationItem.titleView = imageView;
        } else {
            NSLog(@"Error loading navigation bar title image named: %@", imageName);
        }
    }
}