access EXIF data in swift

Question

I try to access Exif data with this sample code :

let fileextension = NSURL(fileURLWithPath: mDir + "/" + f).pathExtension

            if fileextension == "PSD" || fileextension == "NEF" || fileextension == "3FR" || fileextension == "CR2" || fileextension == "DNG" || fileextension == "JPEG" || fileextension == "JPG" || fileextension == "PSB" || fileextension == "RAF" || fileextension == "TIF" {

                let fileattr = try fileManager.attributesOfItem(atPath: mDir + "/" + f)
                let filesize = fileattr[FileAttributeKey.size] as! Int64

                let UrlPath = URL(fileURLWithPath: mDir + "/" + f)
                let imageSource = CGImageSourceCreateWithURL(UrlPath as CFURL, nil)
                let result = CGImageSourceCopyMetadataAtIndex(imageSource!, 0, nil)
                let d = result as! [AnyHashable:Any]
                let tiffDict = d["{TIFF}"] as! [AnyHashable:Any]
                let filedate = tiffDict["DateTime"] as! Date

and I have this error :

Could not cast value of type '__NSCFType' (0x7fff89750188) to 'NSDictionary' (0x7fff89750fe8).

But this sample code work in a playground.

Any explanation ?

Answer 1

To answer the actual question ;), it looks you are calling the wrong function to get it directly as a dictionary, instead of copying metadata using CGImageSourceCopyMetadataAtIndex use CGImageSourceCopyPropertiesAtIndex instead

if let props = CGImageSourceCopyPropertiesAtIndex(imageSource!, 0, nil) as? [String: Any], 
   let tiffData = props["{TIFF}"] {
    print(tiffData)
}

---

Original answer

I used CGImageMetadataCopyTags to extract metadata as an array and then used CGImageMetadataTagCopyName and CGImageMetadataTagCopyValue to map the data into a swift dictionary

let extensions = ["PSD",  "NEF",  "3FR",  "CR2",  "DNG",  "JPEG",  "JPG",  "PSB",  "RAF",  "TIF"]
let fileManager = FileManager.default
let url = URL(fileURLWithPath: mDir + "/" + f)

var metaData = [String: Any]()
if extensions.contains(url.pathExtension) {
    let imageSource = CGImageSourceCreateWithURL(url as CFURL, nil)
    if let result = CGImageSourceCopyMetadataAtIndex(imageSource!, 0, nil) {
        if let array = CGImageMetadataCopyTags(result) as? [CGImageMetadataTag] {
            metaData = array.reduce(into: [String: Any]()) {
                guard let name = CGImageMetadataTagCopyName($1),
                    let value = CGImageMetadataTagCopyValue($1)
                else {
                    return
                }
                $0[String(name)] = value
            }
        }
    }
}

Note that this only gives the tag names like "ShutterSpeedValue", to include the type of tag like "exif", "tiff", "xmp" we can also get the prefix:

guard let prefix = CGImageMetadataTagCopyPrefix($1), 
      let name = CGImageMetadataTagCopyName($1),
      let value = CGImageMetadataTagCopyValue($1)
else { return }

$0["\(prefix):\(name)"] = value