Swift - 使用AVFoundation实现条形码扫描（附：拉近镜头改善读取）

2015-11-22 发布：hangge 阅读：4574

（本文代码已升级至Swift3）

1，条形码（一维码）的扫描读取

原来写过一篇文章，介绍如何使用摄像头扫描读取二维码：Swift - 二维码QRCode的读取（从图片读取，或通过摄像头扫描）要通过摄像头读取条形码，只需要将原来二维码读取代码中 metadataObjectTypes 做如下修改即可：

self.output.metadataObjectTypes = [AVMetadataObjectTypeEAN13Code,
        AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code,
        AVMetadataObjectTypeCode39Code,AVMetadataObjectTypeCode93Code]

2，拉近镜头，改善条形码读取效果

有网友反应，如果条码太小的时候（比如iwatch上支付宝的生成的小条码）就会识别不出来。

解决办法是：像支付宝、QQ一样，通过代码拉近镜头焦距，放大内容区域让机器更好的识别。

下面左图是原始大小，右图将画面放大了1.5倍：

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()
        
        fromCamera()
    }
    
    //通过摄像头扫描
    func fromCamera() {
        do{
            self.device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
            
            self.input = try AVCaptureDeviceInput(device: device)
            
            self.output = AVCaptureMetadataOutput()
            output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            
            self.session = AVCaptureSession()
            if UIScreen.main.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 = [AVMetadataObjectTypeEAN13Code,
                           AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code,
                           AVMetadataObjectTypeCode39Code,AVMetadataObjectTypeCode93Code]
            
            //计算中间可探测区域
            let windowSize = UIScreen.main.bounds.size;
            let scanSize = CGSize(width:windowSize.width*3/4,
                                  height:windowSize.width*3/4)
            var scanRect = CGRect(x:(windowSize.width-scanSize.width)/2,
                                  y:(windowSize.height-scanSize.height)/2,
                                  width:scanSize.width, height:scanSize.height)
            //计算rectOfInterest 注意x,y交换位置
            scanRect = CGRect(x:scanRect.origin.y/windowSize.height,
                              y:scanRect.origin.x/windowSize.width,
                              width:scanRect.size.height/windowSize.height,
                              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.main.bounds
            self.view.layer.insertSublayer(self.preview, at:0)
            
            //添加中间的探测区域绿框
            self.scanRectView = UIView();
            self.view.addSubview(self.scanRectView)
            self.scanRectView.frame = CGRect(x:0, y:0, width:scanSize.width,
                                             height:scanSize.height)
            self.scanRectView.center = CGPoint(x:UIScreen.main.bounds.midX,
                                               y:UIScreen.main.bounds.midY)
            self.scanRectView.layer.borderColor = UIColor.green.cgColor
            self.scanRectView.layer.borderWidth = 1
            
            //开始捕获
            self.session.startRunning()
            
            //放大
            do {
                try self.device!.lockForConfiguration()
            } catch _ {
                NSLog("Error: lockForConfiguration.");
            }
            self.device!.videoZoomFactor = 1.5
            self.device!.unlockForConfiguration()
            
        }catch _ as NSError{
            //打印错误消息
            let alertController = UIAlertController(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",
                    preferredStyle: .alert)
            let cancelAction = UIAlertAction(title: "确定", style: .cancel, handler: nil)
            alertController.addAction(cancelAction)
            self.present(alertController, animated: true, completion: nil)
        }
    }
    
    //摄像头捕获
    func captureOutput(_ captureOutput: AVCaptureOutput!,
                       didOutputMetadataObjects metadataObjects: [Any]!,
                       from 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 alertController = UIAlertController(title: "二维码",
                                    message: stringValue,preferredStyle: .alert)
        let okAction = UIAlertAction(title: "确定", style: .default, handler: {
            action in
            //继续扫描
            self.session.startRunning()
        })
        alertController.addAction(okAction)
        self.present(alertController, animated: true, completion: nil)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}