AVCaptureSession条形码扫描

Question

我目前正在使用AVCaptureSession和AVCaptureMetadataOutput。

它完美无缺，但我只是想知道如何指示仅在AVCaptureVideoPreviewLayer的特定区域扫描和分析元数据对象？

Answer 1

以下是我所拥有的可帮助您走上正确轨道的项目代码示例

    // 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，我有＆＃34; CGAffineTransformInvert：奇异矩阵＆＃34;调用metadataoutputRectOfInterestForRect时出错。我能够在startRunning的{​​{1}}方法之后立即调用它：

AVCaptureSession