Swift如何从UIGraphics将CIFilter应用于UIImage？

我想从

UIImage

创建模糊背景，但收到以下错误：致命错误：在展开可选值时意外发现nil 请帮帮我

func createBackgroundImage(inputImage input:UIImage)->UIImage
{
let bounds = UIScreen.mainScreen().bounds
let size = bounds.size

let scale = max(size.width / input.size.width, size.height / input.size.height)

UIGraphicsBeginImageContextWithOptions(size, false, 1.0 / scale)
input.drawInRect(bounds)

var data:UIImage = UIGraphicsGetImageFromCurrentImageContext()!

UIGraphicsEndImageContext()

var filter = CIFilter(name: "CIGaussianBlur")
filter.setValue(data.CIImage, forKey: kCIInputImageKey)
filter.setValue(10.0, forKey: kCIInputRadiusKey)
return UIImage(CIImage: filter.outputImage)!
}

整个项目可在

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第63行类似于swift-3中关于过滤器的更新：