CIFilter提供了各种各样的滤镜，其中CIQRCodeGenerator可以用来生成二维码。下面通过一个样例演示如何将字符串（链接也是字符串）生成二维码图片，同时支持在二维码中间放置个性化图标。

效果图如下：
原文:Swift - 使用CIFilter生成二维码图片（QRCode）

原文出自：www.hangge.com 转载请保留原文链接：http://www.hangge.com/blog/cache/detail_909.html

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
     
    //不带图片的二维码图片
    let imageViewIcon1 = UIImageView(frame: CGRect(x:20, y:20, width:150, height:150))
    imageViewIcon1.image = createQRForString(qrString: "http://www.hangge.com",
                                             qrImageName: "")
    self.view.addSubview(imageViewIcon1)
     
    //带图片的二维码图片
    let imageViewIcon2 = UIImageView(frame: CGRect(x:200, y:20, width:150, height:150))
    imageViewIcon2.image = createQRForString(qrString: "http://www.hangge.com",
                                             qrImageName: "logo")
    self.view.addSubview(imageViewIcon2)
}
 
//创建二维码图片
func createQRForString(qrString: String?, qrImageName: String?) -> UIImage?{
    if let sureQRString = qrString {
        let stringData = sureQRString.data(using: .utf8,
                                           allowLossyConversion: false)
        // 创建一个二维码的滤镜
        let qrFilter = CIFilter(name: "CIQRCodeGenerator")!
        qrFilter.setValue(stringData, forKey: "inputMessage")
        qrFilter.setValue("H", forKey: "inputCorrectionLevel")
        let qrCIImage = qrFilter.outputImage
         
        // 创建一个颜色滤镜,黑白色
        let colorFilter = CIFilter(name: "CIFalseColor")!
        colorFilter.setDefaults()
        colorFilter.setValue(qrCIImage, forKey: "inputImage")
        colorFilter.setValue(CIColor(red: 0, green: 0, blue: 0), forKey: "inputColor0")
        colorFilter.setValue(CIColor(red: 1, green: 1, blue: 1), forKey: "inputColor1")
         
        // 返回二维码image
        let codeImage = UIImage(ciImage: colorFilter.outputImage!
            .applying(CGAffineTransform(scaleX: 5, y: 5)))
         
        // 通常,二维码都是定制的,中间都会放想要表达意思的图片
        if let iconImage = UIImage(named: qrImageName!) {
            let rect = CGRect(x:0, y:0, width:codeImage.size.width,
                              height:codeImage.size.height)
            UIGraphicsBeginImageContext(rect.size)
             
            codeImage.draw(in: rect)
            let avatarSize = CGSize(width:rect.size.width * 0.25,
                                    height:rect.size.height * 0.25)
            let x = (rect.width - avatarSize.width) * 0.5
            let y = (rect.height - avatarSize.height) * 0.5
            iconImage.draw(in: CGRect(x:x, y:y, width:avatarSize.width,
                                      height:avatarSize.height))
            let resultImage = UIGraphicsGetImageFromCurrentImageContext()
             
            UIGraphicsEndImageContext()
            return resultImage
        }
        return codeImage
    }
    return nil
}
 
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

}