iOS开发-二维码扫描、生成与读取

在iOS7之前，用来扫码可以用第三方库，比如ZXingObjC。在iOS7之后，苹果提供的方法就很方便且高效。

--扫码--

//扫码
-(void)scanBarcode
{
    //初始化捕获设备
    AVCaptureDevice *device=[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    //输入流
    AVCaptureDeviceInput *input=[AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    if (!input) {
        return;
    }

    //输出流
    AVCaptureMetadataOutput *output=[[AVCaptureMetadataOutput alloc]init];
    
    //设置代理 ，主线程刷新
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    
    //自定义一个扫描区域
    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));
    //设置扫描框
    [self setupScanAreaViewWithRect:scanWinRect];
    //设置扫描捕捉数据的框 (此处的屏幕rect值的范围是0-1，按照比例来计算)
    output.rectOfInterest=[self getRectOfInterestWithScanWinRect:scanWinRect];
    
    //初始化连接对象
    AVCaptureSession *session=[[AVCaptureSession alloc]init];
    self.session=session;
    [session setSessionPreset:AVCaptureSessionPresetHigh];
    [session addInput:input];
    [session addOutput:output];
    
    //扫码支持的格式（二维码QR/条形码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];
    
    //开始捕获
    [session startRunning];
}

在设置rectOfInterest值得时候要注意，它是按照屏幕横屏来计算的，所以x轴和y轴要互换，同时注意取值范围值【0-1】，按照屏幕比例计算。

- (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) {
        //结束
        [_session stopRunning];
        //扫码结果
        AVMetadataMachineReadableCodeObject *readObject=[metadataObjects objectAtIndex:0];
        NSLog(@"%@",readObject.stringValue);
    }
}

---

--生成--

    //1.二维码滤镜
    CIFilter *filter=[CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    //2.设置滤镜数据
    [filter setValue:data forKey:@"inputMessage"];

    //3.获取滤镜输出的图像
    CIImage *outputImage=[filter outputImage];

    //将图放大
    CGAffineTransform transform = CGAffineTransformMakeScale(6, 6); // scale 为放大倍数
    CIImage *transformImage = [outputImage imageByApplyingTransform:transform];
    
    //4.转换成CGImage
    CIContext *context=[CIContext contextWithOptions:nil];
    CGImageRef imageRef = [context createCGImage:transformImage fromRect:transformImage.extent];
    //5.转换成UIImage
    UIImage *qrCodeImage = [UIImage imageWithCGImage:imageRef];

• 生成的二维码图片模糊，可将其放大后显示。
• 还可以通过 [CIFilter filterWithName:keysAndValues:, nil] 此滤镜方法修改二维码颜色。

---

--读取--

    //初始化检测器
    CIDetector *detector=[CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}];

    //转成CIImage
    CIImage *ciimage=[CIImage imageWithCGImage:self.image.CGImage];
    
    //检测结果
    NSArray *features =[detector featuresInImage:ciimage];
    CIQRCodeFeature *feature=[features firstObject];

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