Question

basically I am using the example code from http://docs.xamarin.com/ios/recipes/Media/Video_and_Photos/Save_Photo_to_Album_with_Metadata

when I would take a photo and check the files exif data (either through http://exifdata.com/ or Exif-Wizard on the Device), I noticed the exif data did not contain GPS information, so I manually collect the location information, format it, and add it to a dictionary and include that in the meta dictionaries as seen below.

btnCamera.Clicked += delegate {
TweetStation.Camera.TakePicture (this, (obj) => {
var photo = obj.ValueForKey (new NSString ("UIImagePickerControllerOriginalImage")) as    UIImage;
var meta = obj.ValueForKey (new NSString ("UIImagePickerControllerMediaMetadata")) as NSMutableDictionary;

var gpsDict = new NSMutableDictionary ();

...

gpsDict.SetValueForKey (NSObject.FromObject (GpsLong), new NSString ("GPSLongitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLongRef), new NSString ("GPSLongitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLat), new NSString ("GPSLatitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLatRef), new NSString ("GPSLatitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (DateTime.UtcNow.ToString ("HH:MM:ss.ff")),    new NSString ("GPSTimeStamp"));

meta.SetValueForKey (gpsDict, new NSString ("{GPS}"));

Console.WriteLine (meta.Description);

ALAssetsLibrary library = new ALAssetsLibrary ();
library.WriteImageToSavedPhotosAlbum (photo.CGImage, meta, (assetUrl, error) => {

if (error != null) {
Console.WriteLine ("error: "+ error.ToString ());
}
):

Problem is, this doesn’t seem to work, if (error != null) {Console.WriteLine (error.ToString ());} doesn’t print any problems and in the Console.WriteLine (meta.Description); the output is as follows

{
    DPIHeight = 72;
    DPIWidth = 72;
    Orientation = 6;
    "{Exif}" =     {
        ApertureValue = "2.970853654340484";
        BrightnessValue = "1.87496238139573";
        ColorSpace = 1;
        DateTimeDigitized = "2012:08:02 17:12:42";
        DateTimeOriginal = "2012:08:02 17:12:42";
        ExposureMode = 0;
        ExposureProgram = 2;
        ExposureTime = "0.06666666666666667";
        FNumber = "2.8";
        Flash = 24;
        FocalLength = "3.85";
        ISOSpeedRatings =         (
            160
        );
        MeteringMode = 5;
        PixelXDimension = 2592;
        PixelYDimension = 1936;
        SceneType = 1;
        SensingMethod = 2;
        Sharpness = 2;
        ShutterSpeedValue = "3.911199862602335";
        SubjectArea =         (
            1295,
            967,
            699,
            696
        );
        WhiteBalance = 0;
    };
    "{GPS}" =     {
        GPSLatitude = "30.35974270979283";
        GPSLatitudeRef = N;
        GPSLongitude = "91.13930279830274";
        GPSLongitudeRef = W;
        GPSTimeStamp = "22:08:44.66";
    };
    "{TIFF}" =     {
        DateTime = "2012:08:02 17:12:42";
        Make = Apple;
        Model = "iPhone 4";
        Software = "5.0.1";
        XResolution = 72;
        YResolution = 72;
    };
}

showing the gps data.

So, I am curious as to what I am doing wrong, I am very new to monotouch (mac as well) so you’ll forgive the general WTF’ery please.

Answer 1

Also, just FYI, to prevent typos those strings are exposed as the CGImageProperties enum in MonoTouch

// Add GPS metadata, using data in local variables GpsAltitude, GpsLat, GpsLong, etc
gpsDict.SetValueForKey(NSObject.FromObject(GpsAltitude), CGImageProperties.GPSAltitude);
gpsDict.SetValueForKey(NSObject.FromObject(GpsAltitudeRef), CGImageProperties.GPSAltitudeRef);

gpsDict.SetValueForKey(NSObject.FromObject(GpsImgDirection), CGImageProperties.GPSImgDirection);
gpsDict.SetValueForKey(NSObject.FromObject(GpsImgDirectionRef), CGImageProperties.GPSImgDirectionRef);

gpsDict.SetValueForKey (NSObject.FromObject (GpsLong), CGImageProperties.GPSLongitude);
gpsDict.SetValueForKey (NSObject.FromObject (GpsLongRef), CGImageProperties.GPSLongitudeRef);

gpsDict.SetValueForKey (NSObject.FromObject (GpsLat), CGImageProperties.GPSLatitude);
gpsDict.SetValueForKey (NSObject.FromObject (GpsLatRef),CGImageProperties.GPSLatitudeRef);

gpsDict.SetValueForKey (NSObject.FromObject (DateTime.UtcNow.ToString ("HH:MM:ss.ff")), CGImageProperties.GPSTimeStamp);

// Add the GPS data to the metadata
meta.SetValueForKey (gpsDict, CGImageProperties.GPSDictionary);