ios - CIGaussianBlur 图像大小

Question

我想模糊我的 View ，我使用这段代码:

//Get a UIImage from the UIView
NSLog(@"blur capture");
UIGraphicsBeginImageContext(BlurContrainerView.frame.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

//Blur the UIImage
CIImage *imageToBlur = [CIImage imageWithCGImage:viewImage.CGImage];
CIFilter *gaussianBlurFilter = [CIFilter filterWithName: @"CIGaussianBlur"];
[gaussianBlurFilter setValue:imageToBlur forKey: @"inputImage"];
[gaussianBlurFilter setValue:[NSNumber numberWithFloat: 5] forKey: @"inputRadius"]; //change number to increase/decrease blur
CIImage *resultImage = [gaussianBlurFilter valueForKey: @"outputImage"];

//create UIImage from filtered image
blurredImage = [[UIImage alloc] initWithCIImage:resultImage];

//Place the UIImage in a UIImageView
UIImageView *newView = [[UIImageView alloc] initWithFrame:self.view.bounds];
newView.image = blurredImage;

NSLog(@"%f,%f",newView.frame.size.width,newView.frame.size.height);
//insert blur UIImageView below transparent view inside the blur image container
[BlurContrainerView insertSubview:newView belowSubview:transparentView];

它模糊了视野，但不是全部。如何模糊所有 View ？

Answer 1

问题不是它没有模糊所有图像，而是模糊扩展了图像的边界，使图像变大，结果没有正确对齐。

为了保持图像大小相同，在行之后:

CIImage *resultImage    = [gaussianBlurFilter valueForKey: @"outputImage"];

您可以在 resultImage 的中心获取原始图像大小的矩形的 CGRect:

// note, adjust rect because blur changed size of image

CGRect rect             = [resultImage extent];
rect.origin.x          += (rect.size.width  - viewImage.size.width ) / 2;
rect.origin.y          += (rect.size.height - viewImage.size.height) / 2;
rect.size               = viewImage.size;

然后使用 CIContext 获取图像的那部分:

CIContext *context      = [CIContext contextWithOptions:nil];
CGImageRef cgimg        = [context createCGImage:resultImage fromRect:rect];
UIImage   *blurredImage = [UIImage imageWithCGImage:cgimg];
CGImageRelease(cgimg);

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或者，对于 iOS 7，如果您转到 iOS UIImageEffects sample code并下载iOS_UIImageEffects.zip，然后就可以抓取UIImage+ImageEffects类了。无论如何，这提供了一些新方法:

- (UIImage *)applyLightEffect;
- (UIImage *)applyExtraLightEffect;
- (UIImage *)applyDarkEffect;
- (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor;
- (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage;

因此，要对其进行模糊、成像和变亮(产生“毛玻璃”效果)，您可以执行以下操作:

UIImage *newImage = [image applyLightEffect];

有趣的是，Apple 的代码没有使用CIFilter，而是调用了vImageBoxConvolve_ARGB8888。的 vImage high-performance image processing framework . WWDC 2013 视频中说明了此技术 Implementing Engaging UI on iOS .