AVCaptureSession条码扫描

Question

我目前正在使用AVCaptureSession和AVCaptureMetadataOutput。

它工作得很完美，但我只想知道如何仅在AVCaptureVideoPreviewLayer的特定区域上扫描和分析元数据对象。

Answer 1

下面是我的一个项目中的代码示例，它可能会帮助您在正确的轨道上

    // where 'self.session' is previously setup  AVCaptureSession

    // setup metadata capture
    AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
    [self.session addOutput:metadataOutput];
    [metadataOutput setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    [metadataOutput setMetadataObjectTypes:@[AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeEAN13Code]];

    // setup preview layer
    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
    previewLayer.frame = self.previewView.bounds;
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    // we only want the visible area of the previewLayer to accept
    // barcode input (ignore the rest)
    // we need to convert rects coordinate system
    CGRect visibleMetadataOutputRect = [previewLayer metadataOutputRectOfInterestForRect:previewLayer.bounds];
    metadataOutput.rectOfInterest = visibleMetadataOutputRect;

    // add the previewLayer as a sublayer of the displaying UIView
    [self.previewView.layer addSublayer:previewLayer];

Answer 2

在iOS 9.3.2中，调用metadataoutputRectOfInterestForRect时出现了"CGAffineTransformInvert:奇异矩阵“错误。我能够让它在startRunning方法AVCaptureSession之后调用它

captureSession.startRunning()
let visibleRect = previewLayer.metadataOutputRectOfInterestForRect(previewLayer.bounds)
captureMetadataOutput.rectOfInterest = visibleRect