How do I include location data using AVCapturePhoto? - ios

Question

I'm trying to write an iOS app in Swift that will let the user take a photo, and then I'm going to overlay some additional data onto the image. I would like the images to include location data. I'm using AVCapturePhoto, and I can see in the documentation that it has some metadata variables, but I can't find any info on how to use them. When I take a photo now with my app, it has no location data in the EXIF info.
How can I set the capture sessions to embed the location data?

Answer 1

I haven't dealt with the new IOS 11 AVCapturePhoto object so this answer has to make a couple of assumptions about how to access data but in theory all of this should work.
Before adding location data you need to ask the user if you can use their location. Add the "Privacy - Location When In Use" tag to your Info.plist. Then add the following code somewhere in your initialisation.
// Request authorization for location manager
switch CLLocationManager.authorizationStatus() {
case .authorizedWhenInUse:
break
case .notDetermined:
locationManager.requestWhenInUseAuthorization()
locationManagerStatus = CLLocationManager.authorizationStatus()
default:
locationManagerStatus = .denied
}
Now the following will create a dictionary with location information in it.
// create GPS metadata properties
func createLocationMetadata() -> NSMutableDictionary? {
guard CLLocationManager.authorizationStatus() == .authorizedWhenInUse else {return nil}
if let location = locationManager.location {
let gpsDictionary = NSMutableDictionary()
var latitude = location.coordinate.latitude
var longitude = location.coordinate.longitude
var altitude = location.altitude
var latitudeRef = "N"
var longitudeRef = "E"
var altitudeRef = 0
if latitude < 0.0 {
latitude = -latitude
latitudeRef = "S"
}
if longitude < 0.0 {
longitude = -longitude
longitudeRef = "W"
}
if altitude < 0.0 {
altitude = -altitude
altitudeRef = 1
}
let formatter = DateFormatter()
formatter.dateFormat = "yyyy:MM:dd"
gpsDictionary[kCGImagePropertyGPSDateStamp] = formatter.string(from:location.timestamp)
formatter.dateFormat = "HH:mm:ss"
gpsDictionary[kCGImagePropertyGPSTimeStamp] = formatter.string(from:location.timestamp)
gpsDictionary[kCGImagePropertyGPSLatitudeRef] = latitudeRef
gpsDictionary[kCGImagePropertyGPSLatitude] = latitude
gpsDictionary[kCGImagePropertyGPSLongitudeRef] = longitudeRef
gpsDictionary[kCGImagePropertyGPSLongitude] = longitude
gpsDictionary[kCGImagePropertyGPSDOP] = location.horizontalAccuracy
gpsDictionary[kCGImagePropertyGPSAltitudeRef] = altitudeRef
gpsDictionary[kCGImagePropertyGPSAltitude] = altitude
if let heading = locationManager.heading {
gpsDictionary[kCGImagePropertyGPSImgDirectionRef] = "T"
gpsDictionary[kCGImagePropertyGPSImgDirection] = heading.trueHeading
}
return gpsDictionary;
}
return nil
}
This is where I have to do some guessing as I haven't dealt with IOS 11 AVPhotoCapture. You will need a file data representation of your image data. I assume
AVCapturePhoto.fileDataRepresentation()
returns this. Also you will need the original file metadata. I'll take a guess that
AVCapturePhoto.metadata
contains this. With those assumptions the following function will give you a file data representation with additional location data. There may be newer IOS 11 methods to do this in a cleaner way.
func getFileRepresentationWithLocationData(photo : AVCapturePhoto) -> Data {
// get image metadata
var properties = photo.metadata
// add gps data to metadata
if let gpsDictionary = createLocationMetadata() {
properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
}
// create new file representation with edited metadata
return photo.fileDataRepresentation(withReplacementMetadata:properties,
replacementEmbeddedThumbnailPhotoFormat:photo.embeddedThumbnailPhotoFormat,
replacementEmbeddedThumbnailPixelBuffer:photo.previewPixelBuffer,
replacementDepthData:photo.depthData)
}

Answer 2

#adamfowlerphoto gave by far the best answer I could find on this subject!
AVCapturePhoto.fileDataRepresentation(withReplacementMetadata:replacementEmbeddedThumbnailPhotoFormat:replacementEmbeddedThumbnailPixelBuffer:replacementDepthData:)
was deprecated in iOS 12. For the new API you must implement the AVCapturePhotoFileDataRepresentationCustomizerProtocol with the method replacementMetadata(). Here is the updated code:
extension CameraViewController: AVCapturePhotoFileDataRepresentationCustomizer {
// create GPS metadata properties
func createLocationMetadata() -> NSMutableDictionary? {
if let location = locationManager.location {
let gpsDictionary = NSMutableDictionary()
var latitude = location.coordinate.latitude
var longitude = location.coordinate.longitude
var altitude = location.altitude
var latitudeRef = "N"
var longitudeRef = "E"
var altitudeRef = 0
if latitude < 0.0 {
latitude = -latitude
latitudeRef = "S"
}
if longitude < 0.0 {
longitude = -longitude
longitudeRef = "W"
}
if altitude < 0.0 {
altitude = -altitude
altitudeRef = 1
}
let formatter = DateFormatter()
formatter.dateFormat = "yyyy:MM:dd"
gpsDictionary[kCGImagePropertyGPSDateStamp] = formatter.string(from:location.timestamp)
formatter.dateFormat = "HH:mm:ss"
gpsDictionary[kCGImagePropertyGPSTimeStamp] = formatter.string(from:location.timestamp)
gpsDictionary[kCGImagePropertyGPSLatitudeRef] = latitudeRef
gpsDictionary[kCGImagePropertyGPSLatitude] = latitude
gpsDictionary[kCGImagePropertyGPSLongitudeRef] = longitudeRef
gpsDictionary[kCGImagePropertyGPSLongitude] = longitude
gpsDictionary[kCGImagePropertyGPSDOP] = location.horizontalAccuracy
gpsDictionary[kCGImagePropertyGPSAltitudeRef] = altitudeRef
gpsDictionary[kCGImagePropertyGPSAltitude] = altitude
if let heading = locationManager.heading {
gpsDictionary[kCGImagePropertyGPSImgDirectionRef] = "T"
gpsDictionary[kCGImagePropertyGPSImgDirection] = heading.trueHeading
}
return gpsDictionary;
}
return nil
}
func getFileRepresentationWithLocationData(photo : AVCapturePhoto) -> Data {
// get image metadata
var properties = photo.metadata
// add gps data to metadata
if let gpsDictionary = createLocationMetadata() {
properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
}
// create new file representation with edited metadata
return photo.fileDataRepresentation(with: self) ?? Data()
}
func replacementMetadata(for photo: AVCapturePhoto) -> [String : Any]? {
var properties = photo.metadata
// add gps data to metadata
if let gpsDictionary = createLocationMetadata() {
properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
}
return properties
}
}
To print the result you could use this:
static func printEXIFData(imageData: Data) {
var exifData: CFDictionary? = nil
imageData.withUnsafeBytes {
let bytes = $0.baseAddress?.assumingMemoryBound(to: UInt8.self)
if let cfData = CFDataCreate(kCFAllocatorDefault, bytes, imageData.count),
let source = CGImageSourceCreateWithData(cfData, nil) {
exifData = CGImageSourceCopyPropertiesAtIndex(source, 0, nil)
print(exifData)
}
}
}
Don't try to convert your imageData into JPEG representation because it will discard the GPS metadata. (Source: https://stackoverflow.com/a/10339278/647644)
let data = jpegData(compressionQuality: 1.0) // NOOOOO