Swift - 二维码QRCode的读取（从图片读取 ，或通过摄像头扫描）

1，直接读取图片中的二维码

使用 CIDetector 可以很方便的检测并读取二维码。下面是一个从 UIImage 中读取二维码的样例，我们要把图片上所有的二维码信息都打印出来。

代码如下：

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import UIKit   class ViewController: UIViewController {       override func viewDidLoad() {         super.viewDidLoad()           let qrcodeImg =  UIImage(named: "codeBg.png")         let ciImage:CIImage=CIImage(image:qrcodeImg!)!                   let context = CIContext(options: nil)         let detector:CIDetector=CIDetector(ofType: CIDetectorTypeQRCode,             context: context, options: [CIDetectorAccuracy:CIDetectorAccuracyHigh])                   let features=detector.featuresInImage(ciImage)                   print("扫描到二维码个数：\(features.count)")         //遍历所有的二维码，并框出         for feature in features as! [CIQRCodeFeature] {             print(feature.messageString)         }     }       override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()     } }

2，从相册中选择图片读取二维码

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import UIKit   class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {           override func viewDidLoad() {         super.viewDidLoad()     }           //选取相册     @IBAction func fromAlbum(sender: AnyObject) {         //判断设置是否支持图片库         if UIImagePickerController.isSourceTypeAvailable(.PhotoLibrary){             //初始化图片控制器             let picker = UIImagePickerController()             //设置代理             picker.delegate = self             //指定图片控制器类型             picker.sourceType = UIImagePickerControllerSourceType.PhotoLibrary             //弹出控制器，显示界面             self.presentViewController(picker, animated: true, completion: {                 () -> Void in             })         }else{             print("读取相册错误")         }     }           //选择图片成功后代理     func imagePickerController(picker: UIImagePickerController,         didFinishPickingMediaWithInfo info: [String : AnyObject]) {           //获取选择的原图         let image = info[UIImagePickerControllerOriginalImage] as! UIImage                  //二维码读取         let ciImage:CIImage=CIImage(image:image)!         let context = CIContext(options: nil)         let detector:CIDetector=CIDetector(ofType: CIDetectorTypeQRCode,             context: context, options: [CIDetectorAccuracy:CIDetectorAccuracyHigh])         let features=detector.featuresInImage(ciImage)         print("扫描到二维码个数：\(features.count)")         //遍历所有的二维码，并框出         for feature in features as! [CIQRCodeFeature] {             print(feature.messageString)         }                   //图片控制器退出         picker.dismissViewControllerAnimated(true, completion: {             () -> Void in         })     }           override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()     } }

3，使用摄像头扫描读取二维码
（1）扫描主要使用的是 AVFoundation，用起来方便简单
（2）通过 AVCaptureMetadataOutput 的 rectOfInterest 属性，可以设置探测探测区域。同时给这个探测区域添加个方框，只有在框中的二维码才会被扫描到。

代码如下：

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import UIKit import AVFoundation   class ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate, UIAlertViewDelegate{       var scanRectView:UIView!     var device:AVCaptureDevice!     var input:AVCaptureDeviceInput!     var output:AVCaptureMetadataOutput!     var session:AVCaptureSession!     var preview:AVCaptureVideoPreviewLayer!           override func viewDidLoad() {         super.viewDidLoad()     }           //通过摄像头扫描     @IBAction func fromCamera(sender: AnyObject) {         do{             self.device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)                           self.input = try AVCaptureDeviceInput(device: device)                           self.output = AVCaptureMetadataOutput()             output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())                           self.session = AVCaptureSession()             if UIScreen.mainScreen().bounds.size.height<500 {                 self.session.sessionPreset = AVCaptureSessionPreset640x480             }else{                 self.session.sessionPreset = AVCaptureSessionPresetHigh             }                           self.session.addInput(self.input)             self.session.addOutput(self.output)                           self.output.metadataObjectTypes = [AVMetadataObjectTypeQRCode]                           //计算中间可探测区域             let windowSize:CGSize = UIScreen.mainScreen().bounds.size;             let scanSize:CGSize = CGSizeMake(windowSize.width*3/4,                 windowSize.width*3/4);             var scanRect:CGRect = CGRectMake((windowSize.width-scanSize.width)/2,                 (windowSize.height-scanSize.height)/2, scanSize.width, scanSize.height);             //计算rectOfInterest 注意x,y交换位置             scanRect = CGRectMake(scanRect.origin.y/windowSize.height,                 scanRect.origin.x/windowSize.width,                 scanRect.size.height/windowSize.height,                 scanRect.size.width/windowSize.width);             //设置可探测区域             self.output.rectOfInterest = scanRect                           self.preview = AVCaptureVideoPreviewLayer(session:self.session)             self.preview.videoGravity = AVLayerVideoGravityResizeAspectFill             self.preview.frame = UIScreen.mainScreen().bounds             self.view.layer.insertSublayer(self.preview, atIndex:0)                           //添加中间的探测区域绿框             self.scanRectView = UIView();             self.view.addSubview(self.scanRectView)             self.scanRectView.frame = CGRectMake(0, 0, scanSize.width, scanSize.height);             self.scanRectView.center = CGPointMake(                 CGRectGetMidX(UIScreen.mainScreen().bounds),                 CGRectGetMidY(UIScreen.mainScreen().bounds));             self.scanRectView.layer.borderColor = UIColor.greenColor().CGColor             self.scanRectView.layer.borderWidth = 1;                           //开始捕获             self.session.startRunning()         }catch _ as NSError{             //打印错误消息             let errorAlert = UIAlertView(title: "提醒",                 message: "请在iPhone的\"设置-隐私-相机\"选项中,允许本程序访问您的相机",                 delegate: self,                 cancelButtonTitle: "确定")             errorAlert.show()         }     }           //摄像头捕获     func captureOutput(captureOutput: AVCaptureOutput!,         didOutputMetadataObjects metadataObjects: [AnyObject]!,         fromConnection connection: AVCaptureConnection!) {                   var stringValue:String?         if metadataObjects.count > 0 {             let metadataObject = metadataObjects[0] as! AVMetadataMachineReadableCodeObject             stringValue = metadataObject.stringValue                           if stringValue != nil{                 self.session.stopRunning()             }         }         self.session.stopRunning()         //输出结果         let alertView = UIAlertView(title: "二维码", message: stringValue,             delegate: self, cancelButtonTitle: "确定")         alertView.show()     }           //消息框确认后消失     func alertView(alertView: UIAlertView, willDismissWithButtonIndex buttonIndex: Int) {          //继续扫描          self.session.startRunning()     }           override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()     } }