我之前写过一篇文章演示如何实现毛玻璃效果：Swift - 实现毛玻璃效果（Blur、模糊、虚化背景元素）。原理是通过添加一个模糊视图，使得其覆盖下的所有视图都会有模糊效果。

1，效果图

2，样例代码

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var imageView: UIImageView!
    
    @IBOutlet weak var slider: UISlider!
    
    //原图
    lazy var originalImage: UIImage = {
        return UIImage(named: "image1.jpg")
        }()!
    
    lazy var context: CIContext = {
        return CIContext(options: nil)
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    //滑块拖动后
    @IBAction func sliderValueChanged(_ sender: AnyObject) {
        //获取原始图片
        let inputImage =  CIImage(image: originalImage)
        //使用高斯模糊滤镜
        let filter = CIFilter(name: "CIGaussianBlur")!
        filter.setValue(inputImage, forKey:kCIInputImageKey)
        //设置模糊半径值（越大越模糊）
        filter.setValue(slider.value, forKey: kCIInputRadiusKey)
        let outputCIImage = filter.outputImage!
        let rect = CGRect(origin: CGPoint.zero, size: originalImage.size)
        let cgImage = context.createCGImage(outputCIImage, from: rect)
        //显示生成的模糊图片
        imageView.image = UIImage(cgImage: cgImage!)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

源码下载：hangge_1424.zip