GPUImageUIElement -> GPUImageView doesn't work

Question

I'm trying to capture fullscreen video, but first of all wanna capture some simple view. Get image from UIView and produce below view. Here is my code:

- (void)viewDidLoad {
    [super viewDidLoad];

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    label.text = @"fds";
    [self.view addSubview:label];

    handleUiElem = [[GPUImageUIElement alloc] initWithView:label];

    CGRect frame = label.frame;
    frame.origin.y += 100;
    outView = [[GPUImageView alloc] initWithFrame:frame];
    outView.backgroundColor = [UIColor redColor];
    [self.view addSubview:outView];

    [handleUiElem addTarget:outView];
    [[NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(update:) userInfo:nil repeats:YES] fire];
}

- (void)update:(id)timer
{
    [handleUiElem updateUsingCurrentTime];
}

But as are result I get black view instead of text in label. What I'm doing wrong?