iOS Swift。如何从UIImage（NSURL）获取GPS元数据？

Question

Have a reference to an image only having its NSURL. How to get a GPS metadata from it? Of course, I can load a UIImage from NSURL, but then what?

Majority of answers I've found here is regarding UIImagePicker, and using ALAssets then, but I have no such option.

Answer 1

Answering my own question. The memory-effective and fast way to get a GPS metadata is

let options = [kCGImageSourceShouldCache as String: kCFBooleanFalse]
if let data = NSData(contentsOfURL: url), imgSrc = CGImageSourceCreateWithData(data, options) {
    let metadata = CGImageSourceCopyPropertiesAtIndex(imgSrc, 0, options) as Dictionary
    let gpsData = metadata[kCGImagePropertyGPSDictionary] as? [String : AnyObject]
}

The second option is

if let img = CIImage(contentsOfURL: url), metadata = img.properties(), 
gpsData = metadata[kCGImagePropertyGPSDictionary] as? [String : AnyObject] { … }

it looks nicer in Swift but uses more memory (tested via Profiler).

Answer 2

Updated version for Swift 3:

let options = [kCGImageSourceShouldCache as String: kCFBooleanFalse]
if let data = NSData(contentsOfURL: url), let imgSrc = CGImageSourceCreateWithData(data, options as CFDictionary) {
    let metadata = CGImageSourceCopyPropertiesAtIndex(imgSrc, 0, options as CFDictionary) as? [String : AnyObject]
    if let gpsData = metadata?[kCGImagePropertyGPSDictionary as String] {
        //do interesting stuff here
    }
}