在開發中我們用到掃描與拍照的功能是非常的多了，幾乎所有的app都需要拍照的功能了，下面我們來看看Swift二維碼QRCode的讀取（從圖片讀取 ，或通過攝像頭掃描）的例子。

1，直接讀取圖片中的二維碼

使用 CIDetector 可以很方便的檢測並讀取二維碼。下面是一個從 UIImage 中讀取二維碼的樣例，我們要把圖片上所有的二維碼信息都打印出來。

 

 代碼如下 復制代碼 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("掃描到二維碼個數：\(features.count)")
        //遍歷所有的二維碼，並框出
        for feature in features as! [CIQRCodeFeature] {
            print(feature.messageString)
        }
    }
 
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

控制台輸出如下：
掃描到二維碼個數：2
http://www.111cn.net
http://www.111cn.net
可以看到兩個二維碼都成功的讀取到了。

（注：這個我原來用模擬器一直檢測不到二維碼，使用真機調試就沒問題。感謝網友“落葉”的提醒，模擬器選iphone5s及以上設備也是可以檢測到的。）

2，從相冊中選擇圖片讀取二維碼

 代碼如下 復制代碼

import UIKit
 
class ViewController: UIViewController, UIImagePickerControllerDelegate,
UINavigationControllerDelegate {
     
    override func viewDidLoad() {
        super.viewDidLoad()
    }
     
    //選取相冊
    @IBAction func fromAlbum(sender: AnyObject) {
        //判斷設置是否支持圖片庫
        if UIImagePickerController.isSourceTypeAvailable(.PhotoLibrary){
            //初始化圖片控制器
            let picker = UIImagePickerController()
            //設置代理
            picker.delegate = self
            //指定圖片控制器類型
            picker.sourceType = UIImagePickerControllerSourceType.PhotoLibrary
            //彈出控制器，顯示界面
            self.presentViewController(picker, animated: true, completion: {
                () -> Void in
            })
        }else{
            print("讀取相冊錯誤")
        }
    }
     
    //選擇圖片成功後代理
    func imagePickerController(picker: UIImagePickerController,
        didFinishPickingMediaWithInfo info: [String : AnyObject]) {
 
        //獲取選擇的原圖
        let image = info[UIImagePickerControllerOriginalImage] as! UIImage
        
        //二維碼讀取
        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("掃描到二維碼個數：\(features.count)")
        //遍歷所有的二維碼，並框出
        for feature in features as! [CIQRCodeFeature] {
            print(feature.messageString)
        }
         
        //圖片控制器退出
        picker.dismissViewControllerAnimated(true, completion: {
            () -> Void in
        })
    }
     
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

3，使用攝像頭掃描讀取二維碼
（1）掃描主要使用的是 AVFoundation，用起來方便簡單
（2）通過 AVCaptureMetadataOutput 的 rectOfInterest 屬性，可以設置探測探測區域。同時給這個探測區域添加個方框，只有在框中的二維碼才會被掃描到。

效果圖如下：

代碼如下

 

 代碼如下 復制代碼

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()
    }
     
    //通過攝像頭掃描
    @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]
             
            //計算中間可探測區域
            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);
            //計算rectOfInterest 注意x,y交換位置
            scanRect = CGRectMake(scanRect.origin.y/windowSize.height,
                scanRect.origin.x/windowSize.width,
                scanRect.size.height/windowSize.height,
                scanRect.size.width/windowSize.width);
            //設置可探測區域
            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)
             
            //添加中間的探測區域綠框
            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;
             
            //開始捕獲
            self.session.startRunning()
        }catch _ as NSError{
            //打印錯誤消息
            let errorAlert = UIAlertView(title: "提醒",
                message: "請在iPhone的\"設置-隱私-相機\"選項中,允許本程序訪問您的相機",
                delegate: self,
                cancelButtonTitle: "確定")
            errorAlert.show()
        }
    }
     
    //攝像頭捕獲
    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()
        //輸出結果
        let alertView = UIAlertView(title: "二維碼", message: stringValue,
            delegate: self, cancelButtonTitle: "確定")
        alertView.show()
    }
     
    //消息框確認後消失
    func alertView(alertView: UIAlertView, willDismissWithButtonIndex buttonIndex: Int) {
         //繼續掃描
         self.session.startRunning()
    }
     
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}