A way to show a transparent modal view controller. It's not really transparent, the modal just uses a screenshot as its background.

TransparentModalViewController.m

- (void)showCard:(id)sender
{
    UIGraphicsBeginImageContext(self.view.window.frame.size);
    [self.view.window.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    UIViewControllerSubclass *card = [[UIViewControllerSubclass alloc] init];
    card.background = screenshot;
    [self presentModalViewController:card animated:NO];
}