使用iOS 7的快照API模糊屏幕

问题描述

我相信NDA会下降，所以我可以问这个问题。我有一个UIView子类：

I believe the NDA is down, so I can ask this question. I have a UIView subclass:

BlurView *blurredView = ((BlurView *)[self.view snapshotViewAfterScreenUpdates:NO]);
blurredView.frame = self.view.frame;
[self.view addSubview:blurredView];

到目前为止，它在捕获屏幕方面做得很好，但现在我想模糊那个视图。我到底该怎么做？根据我的阅读，我需要捕获视图的当前内容（上下文？！）并将其转换为CIImage（没有？），然后对其应用CIGaussianBlur并将其绘制回视图。

It does its job so far in capturing the screen, but now I want to blur that view. How exactly do I go about this? From what I've read I need to capture the current contents of the view (context?!) and convert it to CIImage (no?) and then apply a CIGaussianBlur to it and draw it back on the view.

我该怎么做？

PS该视图不是动画，所以它应该是性能明智的。

P.S. The view is not animated, so it should be OK performance wise.

编辑：这是我到目前为止所拥有的。问题是我无法将快照捕获到UIImage，我得到一个黑屏。但如果我直接将视图添加为子视图，我可以看到快照在那里。

Here is what I have so far. The problem is that I can't capture the snapshot to a UIImage, I get a black screen. But if I add the view as a subview directly, I can see the snapshot is there.

// Snapshot
UIView *view = [self.view snapshotViewAfterScreenUpdates:NO];

// Convert to UIImage
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// Apply the UIImage to a UIImageView
BlurView *blurredView = [[BlurView alloc] initWithFrame:CGRectMake(0, 0, 500, 500)];
[self.view addSubview:blurredView];
blurredView.imageView.image = img;

// Black screen -.-

BlurView.m：

BlurView.m:

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];

    if (self) {
        // Initialization code
        self.imageView = [[UIImageView alloc] init];
        self.imageView.frame = CGRectMake(20, 20, 200, 200);
        [self addSubview:self.imageView];
    }
    return self;
}

推荐答案

来自WWDC的示例代码

Sample Code from WWDC ios_uiimageeffects

有a UIImage 类别名为 UIImage + ImageEffects

这是它的API：

- (UIImage *)applyLightEffect;
- (UIImage *)applyExtraLightEffect;
- (UIImage *)applyDarkEffect;
- (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor;

- (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius
                       tintColor:(UIColor *)tintColor
           saturationDeltaFactor:(CGFloat)saturationDeltaFactor
                       maskImage:(UIImage *)maskImage;

由于法律原因，我无法在此处显示实施，其中有一个演示项目。应该很容易开始。

For legal reason I can't show the implementation here, there is a demo project in it. should be pretty easy to get start with.

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