在iOS7之前，用來(lái)掃碼可以用第三方庫(kù)，比如ZXingObjC。在iOS7之后，蘋(píng)果提供的方法就很方便且高效。

--掃碼--

//掃碼
-(void)scanBarcode
{
    //初始化捕獲設(shè)備
    AVCaptureDevice *device=[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    //輸入流
    AVCaptureDeviceInput *input=[AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    if (!input) {
        return;
    }

    //輸出流
    AVCaptureMetadataOutput *output=[[AVCaptureMetadataOutput alloc]init];
    
    //設(shè)置代理 ，主線程刷新
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    
    //自定義一個(gè)掃描區(qū)域
    CGRect scanWinRect=CGRectMake(self.view.width/6, (self.view.height-self.view.width)/2+self.view.width/6, (self.view.width-self.view.width/3), (self.view.width-self.view.width/3));
    //設(shè)置掃描框
    [self setupScanAreaViewWithRect:scanWinRect];
    //設(shè)置掃描捕捉數(shù)據(jù)的框 (此處的屏幕rect值的范圍是0-1，按照比例來(lái)計(jì)算)
    output.rectOfInterest=[self getRectOfInterestWithScanWinRect:scanWinRect];
    
    //初始化連接對(duì)象
    AVCaptureSession *session=[[AVCaptureSession alloc]init];
    self.session=session;
    [session setSessionPreset:AVCaptureSessionPresetHigh];
    [session addInput:input];
    [session addOutput:output];
    
    //掃碼支持的格式（二維碼QR/條形碼EAN）
    output.metadataObjectTypes = @[AVMetadataObjectTypeQRCode,AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code];
    
    AVCaptureVideoPreviewLayer *layer=[AVCaptureVideoPreviewLayer layerWithSession:session];
    layer.videoGravity=AVLayerVideoGravityResizeAspectFill;
    layer.frame=self.view.layer.bounds;
    [self.view.layer insertSublayer:layer atIndex:0];
    
    //開(kāi)始捕獲
    [session startRunning];
}

在設(shè)置rectOfInterest值得時(shí)候要注意，它是按照屏幕橫屏來(lái)計(jì)算的，所以x軸和y軸要互換，同時(shí)注意取值范圍值【0-1】，按照屏幕比例計(jì)算。

- (CGRect)getRectOfInterestWithScanWinRect:(CGRect )rect
{
    CGFloat x = rect.origin.x/self.view.width;
    CGFloat y = rect.origin.y/self.view.height;
    CGFloat width=rect.size.width/self.view.width;
    CGFloat height=rect.size.height/self.view.height;

    return CGRectMake(y, x, height, width);
}

代理方法：

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
    if (metadataObjects.count>0) {
        //結(jié)束
        [_session stopRunning];
        //掃碼結(jié)果
        AVMetadataMachineReadableCodeObject *readObject=[metadataObjects objectAtIndex:0];
        NSLog(@"%@",readObject.stringValue);
    }
}

--生成--

    //1.二維碼濾鏡
    CIFilter *filter=[CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    //2.設(shè)置濾鏡數(shù)據(jù)
    [filter setValue:data forKey:@"inputMessage"];

    //3.獲取濾鏡輸出的圖像
    CIImage *outputImage=[filter outputImage];

    //將圖放大
    CGAffineTransform transform = CGAffineTransformMakeScale(6, 6); // scale 為放大倍數(shù)
    CIImage *transformImage = [outputImage imageByApplyingTransform:transform];
    
    //4.轉(zhuǎn)換成CGImage
    CIContext *context=[CIContext contextWithOptions:nil];
    CGImageRef imageRef = [context createCGImage:transformImage fromRect:transformImage.extent];
    //5.轉(zhuǎn)換成UIImage
    UIImage *qrCodeImage = [UIImage imageWithCGImage:imageRef];

• 生成的二維碼圖片模糊，可將其放大后顯示。
• 還可以通過(guò) [CIFilter filterWithName:keysAndValues:, nil] 此濾鏡方法修改二維碼顏色。

--讀取--

    //初始化檢測(cè)器
    CIDetector *detector=[CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}];

    //轉(zhuǎn)成CIImage
    CIImage *ciimage=[CIImage imageWithCGImage:self.image.CGImage];
    
    //檢測(cè)結(jié)果
    NSArray *features =[detector featuresInImage:ciimage];
    CIQRCodeFeature *feature=[features firstObject];

    //打印
    NSString *string=[feature messageString];