全屏高斯模糊

Question

我想模糊我的 iOS 应用的整个屏幕，我不能使用UIBlurEffect，因为我希望能够控制模糊。所以我尝试使用CIGaussianBlur，但屏幕边缘出现问题。

我正在截取屏幕截图，然后通过CIFilter 和CIGaussianBlur 运行它，将CIImage 转换回UIImage，并在屏幕顶​​部添加新的模糊图像。

这是我的代码：

    let layer = UIApplication.sharedApplication().keyWindow?.layer
    UIGraphicsBeginImageContext(view.frame.size)

    layer!.renderInContext(UIGraphicsGetCurrentContext()!)
    let screenshot = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    let blurRadius = 5
    var ciimage: CIImage = CIImage(image: screenshot)!
    var filter: CIFilter = CIFilter(name:"CIGaussianBlur")!
    filter.setDefaults()
    filter.setValue(ciimage, forKey: kCIInputImageKey)
    filter.setValue(blurRadius, forKey: kCIInputRadiusKey)

    let ciContext = CIContext(options: nil)
    let result = filter.valueForKey(kCIOutputImageKey) as! CIImage!
    let cgImage = ciContext.createCGImage(result, fromRect: view.frame)

    let finalImage = UIImage(CGImage: cgImage)


    let blurImageView = UIImageView(frame: view.frame)
    blurImageView.image = finalImage
    blurImageView.sizeToFit()
    blurImageView.contentMode = .ScaleAspectFit
    blurImageView.center = view.center
    view.addSubview(blurImageView)

这是我看到的：

它看起来几乎正确，除了边缘。似乎模糊度正在从模糊半径到边缘起飞。我尝试使用上下文大小，但似乎无法使其工作。

如何让模糊一直到边缘？

Answer 1

这是因为高斯模糊滤镜对图像边缘之外的像素进行采样。但是因为没有像素，你会得到这个奇怪的伪像。您可以使用"CIAffineClamp" 过滤器在各个方向上无限“扩展”您的图像。

请看这个答案https://stackoverflow.com/a/18138742/762779

我尝试使用链接的“CIAffineClamp-> CIGaussianBlur”过滤器运行您的代码，并获得了不错的结果。

let layer = UIApplication.sharedApplication().keyWindow?.layer
UIGraphicsBeginImageContext(view.frame.size)

layer!.renderInContext(UIGraphicsGetCurrentContext()!)
let screenshot = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

let blurRadius = 5
let ciimage: CIImage = CIImage(image: screenshot)!

// Added "CIAffineClamp" filter 
let affineClampFilter = CIFilter(name: "CIAffineClamp")!
affineClampFilter.setDefaults()
affineClampFilter.setValue(ciimage, forKey: kCIInputImageKey)
let resultClamp = affineClampFilter.valueForKey(kCIOutputImageKey)

// resultClamp is used as input for "CIGaussianBlur" filter
let filter: CIFilter = CIFilter(name:"CIGaussianBlur")!
filter.setDefaults()
filter.setValue(resultClamp, forKey: kCIInputImageKey)
filter.setValue(blurRadius, forKey: kCIInputRadiusKey)


let ciContext = CIContext(options: nil)
let result = filter.valueForKey(kCIOutputImageKey) as! CIImage!
let cgImage = ciContext.createCGImage(result, fromRect: ciimage.extent) // changed to ciiimage.extend 

let finalImage = UIImage(CGImage: cgImage)

let blurImageView = UIImageView(frame: view.frame)
blurImageView.image = finalImage
blurImageView.sizeToFit()
blurImageView.contentMode = .ScaleAspectFit
blurImageView.center = view.center
view.addSubview(blurImageView)