如何用元数据丰富UIImage数据

var imageWithMetadata = UIImage(data: imageData)?.mutableCopy() as? NSMutableData

let metadata = NSMutableDictionary()
metadata.setValue("My Image", forKey: kCGImagePropertyTIFFDictionary as String)
metadata.setValue("1.0", forKey: kCGImagePropertyTIFFVersion as String)
// 添加更多的元数据信息...

imageWithMetadata?.setValue(metadata, forKey: kCGImagePropertyTIFFDictionary as String)

let finalImageData = UIImagePNGRepresentation(imageWithMetadata as! UIImage)