detecting if iPhone is in a dark room

Question

Is there a way to use the iPhone proximity sensor to detect whether the phone is in a room with no light?

This question seems to imply that this is not possible...Do

Answer 1

Swift 4.2 version based upon Wildaker's code. Xcode 10 refused to allow it to be a Float, but the double has worked.

func getBrightness(sampleBuffer: CMSampleBuffer) -> Double {
    let rawMetadata = CMCopyDictionaryOfAttachments(allocator: nil, target: sampleBuffer, attachmentMode: CMAttachmentMode(kCMAttachmentMode_ShouldPropagate))
    let metadata = CFDictionaryCreateMutableCopy(nil, 0, rawMetadata) as NSMutableDictionary
    let exifData = metadata.value(forKey: "{Exif}") as? NSMutableDictionary
    let brightnessValue : Double = exifData?[kCGImagePropertyExifBrightnessValue as String] as! Double
    return brightnessValue
}