图片高斯模糊

用系统的CIFilter实现

 // blur value:0 - 3
  @IBAction func sliderValueChanged(_ sender: UISlider) {

      let originImage = CIImage(cgImage: self.originImage.cgImage! )
      //创建高斯模糊滤镜
      let filter = CIFilter(name: "CIGaussianBlur")
      filter!.setValue(originImage, forKey: kCIInputImageKey)
      filter!.setValue(NSNumber(value: sender.value * 3), forKey: kCIInputRadiusKey)

      //生成模糊图片
      let context = CIContext(options: nil)

      let outputCIImage = filter!.outputImage!
      let rect = CGRect(origin: CGPoint.zero, size: self.originImage.size)

      let blurCGImage = context.createCGImage(outputCIImage, from: rect)!
      let blurImage = UIImage(cgImage: blurCGImage)
      // do something with blurImage
  }