GPUImage 动画高斯模糊滤镜

我使用 GPUImage 高斯模糊滤镜来模糊静态图像。我想将模糊大小与 UI 元素联系起来，当用户更改该元素时，我会模糊图片。我现在的做法是，当发生重大（> 0.25）变化时，更改blurSize，重新应用滤镜并将新图像动画化到imageView中。

有没有更有效的方法让我这样做？

在 iPhone 5 上，虽然性能并不滞后，但也不是超级流畅（但也许这是因为此操作成本太高，无法实现超级流畅）。

有趣的问题。最好的选择是在您的范围内以几个模糊比例预先计算和渲染 CGImage，然后使用两个堆叠的 UIImageView，其中顶部的一个显示较模糊的副本但部分透明。例如，如果您在半径 1,2,3,…,10 处进行模糊渲染，并且想要显示 3.7，则可以在底部显示图像 3，在顶部显示图像 4，不透明度为 70%。

// Created in answer to Nikhil Varma's question at http://stackoverflow.com/questions/18804668/gpuimage-animated-gaussian-blur-filter
#import "GPUImage.h"
#define BLUR_STEP 2.
@interface AHViewController : UIViewController

@property (weak, nonatomic) IBOutlet UIImageView *imageView2;
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property (nonatomic) CGFloat blurRadius;
@property (nonatomic, strong) UIImage *image;
@property (nonatomic, strong) GPUImageGaussianBlurFilter *blurFilter;
@property (nonatomic, strong) NSCache *blurredImageCache;
@property (nonatomic, strong) dispatch_queue_t blurQueue;
@property (nonatomic, strong) NSMutableSet *blurAmountsBeingRendered;
@end

@implementation AHViewController

-(void)viewDidLoad {
    [super viewDidLoad];
    self.image = [UIImage imageNamed:@"ph.jpg"];
    self.blurFilter = [GPUImageGaussianBlurFilter new];
    self.blurredImageCache = [NSCache new];
    self.blurQueue = dispatch_queue_create("Image Blur Queue", DISPATCH_QUEUE_SERIAL);
    self.blurAmountsBeingRendered = [NSMutableSet set];
    self.blurRadius = 1.0;
}
- (IBAction)sliderDidMove:(UISlider *)sender {
    self.blurRadius = 10 * sender.value;
}
-(void)setBlurRadius:(CGFloat)blurRadius {
    _blurRadius = blurRadius;
    CGFloat smaller = self.blurRadius - fmodf(self.blurRadius, BLUR_STEP);
    [self asyncGenerateImageWithBlurAmount:smaller];
    CGFloat larger = smaller + BLUR_STEP;
    [self asyncGenerateImageWithBlurAmount:larger];

}
-(UIImage *)cachedImageWithBlurAmount:(CGFloat)blur {
    return [self.blurredImageCache objectForKey:@(blur)];
}
-(void)asyncGenerateImageWithBlurAmount:(CGFloat)blur {
    // This image is already available.
    if([self.blurredImageCache objectForKey:@(blur)]) {
        [self imageIsAvailableWithBlur:blur];
        return;
    }
    // There's already a render going on for this. Just return.
    if([self.blurAmountsBeingRendered containsObject:@(blur)])
        return;

    // Start a render
    [self.blurAmountsBeingRendered addObject:@(blur)];
    dispatch_async(self.blurQueue, ^{
        self.blurFilter.blurSize = blur;
        UIImage *result = [self.blurFilter imageByFilteringImage:self.image];
        [self.blurredImageCache setObject:result forKey:@(blur)];
        [self.blurAmountsBeingRendered removeObject:@(blur)];
        dispatch_async(dispatch_get_main_queue(), ^{
            [self imageIsAvailableWithBlur:blur];
        });
    });
}

-(void)imageIsAvailableWithBlur:(CGFloat)blurAmount {
    CGFloat smaller = self.blurRadius - fmodf(self.blurRadius, BLUR_STEP);
    CGFloat larger = smaller + BLUR_STEP;

    UIImage *sharperImage = [self cachedImageWithBlurAmount:smaller];
    UIImage *blurrier = [self cachedImageWithBlurAmount:larger];
    if(sharperImage && blurrier) {
        if(![self.imageView.image isEqual:sharperImage])
            self.imageView.image = sharperImage;
        if(![self.imageView2.image isEqual:blurrier]) {
            self.imageView2.image = blurrier;
        }
        self.imageView2.alpha = (self.blurRadius - smaller) / BLUR_STEP;
    }
}


@end