GPUImage图片添加水印

    UILabel *lab = [[UILabel alloc] initWithFrame:CGRectMake(100, 480, 120, 20)];
    lab.text = @"滤镜信息";
    lab.font = [UIFont systemFontOfSize:20];
    lab.textColor = [UIColor redColor];
    lab.backgroundColor = [UIColor clearColor];
    UIView *view = [[UIView alloc] initWithFrame:self.view.bounds];
    [view addSubview:lab];
    GPUImageUIElement *uiElement = [[GPUImageUIElement alloc] initWithView:view];
    

    UIImage *inputImage = [UIImage imageNamed:@"Lambeau.jpg"];
    
    GPUImageFilter *disFilter = [[GPUImageFilter alloc] init];
    [disFilter forceProcessingAtSize:inputImage.size];
    [disFilter useNextFrameForImageCapture];
    
    GPUImagePicture *sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage];
    
    [sourcePicture addTarget:disFilter];
    
     GPUImageAlphaBlendFilter *_filter = [[GPUImageAlphaBlendFilter alloc] init];
    _filter.mix = 1;
    [disFilter addTarget:_filter];
    [uiElement addTarget:_filter];
    
     [uiElement update];
    [sourcePicture processImageUpToFilter:_filter withCompletionHandler:^(UIImage *processedImage) {
        
        dispatch_async(dispatch_get_main_queue(), ^{
            UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
            imageView.image = processedImage;
            [self.view addSubview:imageView];
        });

    }];