工作需要寫了個二維碼掃描的框架私爷，識別光線強度是否開啟手電筒，項目地址：https://github.com/GitZhouQi/QRCode
光線識別：
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
}