Ios 使用GPUImage筛选实时视图

我试图使用GPUImage来过滤视图，因为它是在一种iOS7风格的覆盖中更新的。为此，我在NSTimer上运行以下代码，但是我的NSLog显示，

[self.backgroundUIImage imageFromCurrentlyProcessedOutput]

正在返回（null）。我知道视图self.background在添加到视图中时工作正常（self.finalImageView也已添加到视图中）。我不确定我是否以正确的方式进行这项工作，因为在GPUImage github页面上没有关于如何进行这项工作的真正文档。有人知道这样使用GPUImage是否可行吗

if (!self.backgroundUIImage) {

        self.backgroundUIImage = [[GPUImageUIElement alloc] initWithView:self.background];

        GPUImageFastBlurFilter *fastBlur = [[GPUImageFastBlurFilter alloc] init];
        fastBlur.blurSize = 0.5;
        [self.backgroundUIImage addTarget:fastBlur];
        [self.backgroundUIImage update];

    }

    [self.backgroundUIImage update];

    NSLog(@"image : %@",[self.backgroundUIImage imageFromCurrentlyProcessedOutput]);

    self.finalImageView.image = [self.backgroundUIImage imageFromCurrentlyProcessedOutput];

    [self bringSubviewToFront:self.finalImageView];

编辑1

我现在已经看了FilterShowcase示例代码，因此我现在尝试实现live blur，如下所示：

NSLog(@"regenerating view");

    if (!self.backgroundUIImage) {

        GPUImageAlphaBlendFilter *blendFilter = [[GPUImageAlphaBlendFilter alloc] init];
        blendFilter.mix = 1.0;

        self.backgroundUIImage = [[GPUImageUIElement alloc] initWithView:self.background];

        NSLog(@"self.backgroundUIImage : %@",self.backgroundUIImage);

        self.filter = [[GPUImageFastBlurFilter alloc] init];
        self.filter.blurSize = 10;

        [self.filter addTarget:blendFilter];
        [self.backgroundUIImage addTarget:blendFilter];

        [blendFilter addTarget:self.finalImageView];

        __unsafe_unretained GPUImageUIElement *weakUIElementInput = self.backgroundUIImage;

        [self.filter setFrameProcessingCompletionBlock:^(GPUImageOutput * filter, CMTime frameTime){

            [weakUIElementInput update];

        }];

    }

    __unsafe_unretained GPUImageUIElement *weakUIElementInput = self.backgroundUIImage;

    [self.filter setFrameProcessingCompletionBlock:^(GPUImageOutput * filter, CMTime frameTime){

        [weakUIElementInput update];

    }];

    [self bringSubviewToFront:self.finalImageView];

@property (nonatomic, strong) GPUImageView *finalImageView;
@property (nonatomic, strong) SMBouncingBubblesBackground *background;

@property (nonatomic, strong) GPUImageUIElement *backgroundUIImage;
@property (nonatomic, strong) GPUImageFastBlurFilter *filter;

其中@properties设置如下：

NSLog(@"regenerating view");

    if (!self.backgroundUIImage) {

        GPUImageAlphaBlendFilter *blendFilter = [[GPUImageAlphaBlendFilter alloc] init];
        blendFilter.mix = 1.0;

        self.backgroundUIImage = [[GPUImageUIElement alloc] initWithView:self.background];

        NSLog(@"self.backgroundUIImage : %@",self.backgroundUIImage);

        self.filter = [[GPUImageFastBlurFilter alloc] init];
        self.filter.blurSize = 10;

        [self.filter addTarget:blendFilter];
        [self.backgroundUIImage addTarget:blendFilter];

        [blendFilter addTarget:self.finalImageView];

        __unsafe_unretained GPUImageUIElement *weakUIElementInput = self.backgroundUIImage;

        [self.filter setFrameProcessingCompletionBlock:^(GPUImageOutput * filter, CMTime frameTime){

            [weakUIElementInput update];

        }];

    }

    __unsafe_unretained GPUImageUIElement *weakUIElementInput = self.backgroundUIImage;

    [self.filter setFrameProcessingCompletionBlock:^(GPUImageOutput * filter, CMTime frameTime){

        [weakUIElementInput update];

    }];

    [self bringSubviewToFront:self.finalImageView];

@property (nonatomic, strong) GPUImageView *finalImageView;
@property (nonatomic, strong) SMBouncingBubblesBackground *background;

@property (nonatomic, strong) GPUImageUIElement *backgroundUIImage;
@property (nonatomic, strong) GPUImageFastBlurFilter *filter;

这看起来好像没有生成图像，因为我可以通过self.finalImageView看到背景视图。关于如何做到这一点的一些文档将非常棒