Swift版二维码扫描，识别光线强度是否开启手电筒

工作需要写了个二维码扫描的框架，识别光线强度是否开启手电筒，项目地址：https://github.com/GitZhouQi/QRCode

光线识别：

public func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        
        guard let metadataDict: CFDictionary = CMCopyDictionaryOfAttachments(nil, sampleBuffer, kCMAttachmentMode_ShouldPropagate) else { return }
        guard let metadata = metadataDict as? [AnyHashable: Any] else { return }
        var brightnessValue: Float = 0
        guard let exifMetadata = (metadata[(kCGImagePropertyExifDictionary as String)]) as? [AnyHashable: Any] else { return }
        guard let brightness = exifMetadata["BrightnessValue"] as? NSNumber else { return }
        brightnessValue = brightness.floatValue
    }