CIGaussianBlur 图像大小

Question

我想模糊我的视野，我使用以下代码：

//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];

它模糊了视图，但不是全部。如何模糊所有视图？

Answer 1

问题不在于它没有模糊整个图像，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。

为了保持图片大小不变，行后：

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

您可以在resultImage 的中心抓取一个与原始图像大小相同的矩形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 抓取图像的那部分：

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

---

或者，对于 iOS 7，如果您转到 iOS UIImageEffects sample code 并下载 iOS_UIImageEffects.zip，则可以获取 UIImage+ImageEffects 类别。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，要模糊和成像并使其变亮（给出“毛玻璃”效果），您可以这样做：

UIImage *newImage = [image applyLightEffect];

有趣的是，Apple 的代码并没有使用CIFilter，而是调用vImage high-performance image processing framework 中的vImageBoxConvolve_ARGB8888。该技术在 WWDC 2013 视频Implementing Engaging UI on iOS 中有说明。

Answer 2

更快的解决方案是完全避免 CGImageRef 并在 CIImage 惰性级别执行所有转换。

所以，而不是你的不合适：

// create UIImage from filtered image (but size is wrong)
blurredImage = [[UIImage alloc] initWithCIImage:resultImage];

一个很好的解决方案是这样写：

目标-C

// cropping rect because blur changed size of image
CIImage *croppedImage = [resultImage imageByCroppingToRect:imageToBlur.extent];
// create UIImage from filtered cropped image
blurredImage = [[UIImage alloc] initWithCIImage:croppedImage];

斯威夫特 3

// cropping rect because blur changed size of image
let croppedImage = resultImage.cropping(to: imageToBlur.extent)
// create UIImage from filtered cropped image
let blurredImage = UIImage(ciImage: croppedImage)

斯威夫特 4

// cropping rect because blur changed size of image
let croppedImage = resultImage.cropped(to: imageToBlur.extent)
// create UIImage from filtered cropped image
let blurredImage = UIImage(ciImage: croppedImage)

Answer 3

看起来模糊滤镜返回的图像比您开始使用的图像更大，这是有道理的，因为边缘处的像素在它们之外变得模糊。最简单的解决方案可能是让newView 使用contentMode 或UIViewContentModeCenter，这样它就不会试图压扁模糊的图像；您还可以通过将blurredImage 绘制在适当大小的新上下文的中心来裁剪blurredImage，但您实际上并不需要这样做。