Después de innumerables intentos y examinar cada resultado de SO answer + google, me desconcierta que trabajar con EXIF ​​en iOS sea tan frustrante.

A continuación se muestra el código de trabajo con sus resultados.

[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:videoConnection
    completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error)
    {
        NSData *imageNSData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];

        CGImageSourceRef imgSource = CGImageSourceCreateWithData((__bridge_retained CFDataRef)imageNSData, NULL);

        //get all the metadata in the image
        NSDictionary *metadata = (__bridge NSDictionary *)CGImageSourceCopyPropertiesAtIndex(imgSource, 0, NULL);

        NSLog(@"original metadata Info: %@",metadata);

        //make the metadata dictionary mutable so we can add properties to it
        NSMutableDictionary *metadataAsMutable = [metadata mutableCopy];

        NSMutableDictionary *EXIFDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyExifDictionary]mutableCopy];
        NSMutableDictionary *GPSDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyGPSDictionary]mutableCopy];
        NSMutableDictionary *RAWDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyRawDictionary]mutableCopy];

        if(!EXIFDictionary)
            EXIFDictionary = [[NSMutableDictionary dictionary] init];

        if(!GPSDictionary)
            GPSDictionary = [[NSMutableDictionary dictionary] init];

        if(!RAWDictionary)
            RAWDictionary = [[NSMutableDictionary dictionary] init];


        [GPSDictionary setObject:@"camera coord Latitude"
                         forKey:(NSString*)kCGImagePropertyGPSLatitude];
        [GPSDictionary setObject:@"camera coord Longitude"
                         forKey:(NSString*)kCGImagePropertyGPSLongitude];
        [GPSDictionary setObject:@"camera GPS Date Stamp"
                         forKey:(NSString*)kCGImagePropertyGPSDateStamp];
        [GPSDictionary setObject:@"camera direction (heading) in degrees"
                         forKey:(NSString*)kCGImagePropertyGPSImgDirection];

        [GPSDictionary setObject:@"subject coord Latitude"
                         forKey:(NSString*)kCGImagePropertyGPSDestLatitude];
        [GPSDictionary setObject:@"subject coord Longitude"
                         forKey:(NSString*)kCGImagePropertyGPSDestLongitude];

        [EXIFDictionary setObject:@"[S.D.] kCGImagePropertyExifUserComment"
                           forKey:(NSString *)kCGImagePropertyExifUserComment];

        [EXIFDictionary setValue:@"69 m" forKey:(NSString *)kCGImagePropertyExifSubjectDistance];


        //Add the modified Data back into the image’s metadata
        [metadataAsMutable setObject:EXIFDictionary forKey:(NSString *)kCGImagePropertyExifDictionary];
        [metadataAsMutable setObject:GPSDictionary forKey:(NSString *)kCGImagePropertyGPSDictionary];
        [metadataAsMutable setObject:RAWDictionary forKey:(NSString *)kCGImagePropertyRawDictionary];


        NSLog(@"metadataAsMutable Info: %@",metadataAsMutable);

        CFStringRef UTI = CGImageSourceGetType(imgSource); //this is the type of image (e.g., public.jpeg)

        //this will be the data CGImageDestinationRef will write into
        NSMutableData *newImageData = [NSMutableData data];

        CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)newImageData, UTI, 1, NULL);

        if(!destination)
            NSLog(@"***Could not create image destination ***");

        //add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
        CGImageDestinationAddImageFromSource(destination, imgSource, 0, (__bridge CFDictionaryRef) metadataAsMutable);

        //tell the destination to write the image data and metadata into our data object.
        //It will return false if something goes wrong
        BOOL success = NO;
        success = CGImageDestinationFinalize(destination);

        if(!success)
            NSLog(@"***Could not create data from image destination ***");

        CIImage *testImage = [CIImage imageWithData:newImageData];
        NSDictionary *propDict = [testImage properties];
        NSLog(@"Properties %@", propDict);

    }];

Que produce esto:

2012-10-12 23:17:45.415 Waypointer[3120:907] original metadata Info: {
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 1;
PixelHeight = 2448;
PixelWidth = 3264;
"{Exif}" =     {
    ApertureValue = "2.526069";
    BrightnessValue = "-4.410617";
    ColorSpace = 1;
    ComponentsConfiguration =         (
        1,
        2,
        3,
        0
    );
    ExifVersion =         (
        2,
        2,
        1
    );
    ExposureMode = 0;
    ExposureProgram = 2;
    ExposureTime = "0.06666667";
    FNumber = "2.4";
    Flash = 16;
    FlashPixVersion =         (
        1,
        0
    );
    FocalLenIn35mmFilm = 35;
    FocalLength = "4.28";
    ISOSpeedRatings =         (
        800
    );
    MeteringMode = 5;
    PixelXDimension = 3264;
    PixelYDimension = 2448;
    SceneCaptureType = 0;
    SensingMethod = 2;
    ShutterSpeedValue = "3.906905";
    SubjectArea =         (
        1631,
        1223,
        881,
        881
    );
    WhiteBalance = 0;
};
"{TIFF}" =     {
    Orientation = 1;
    ResolutionUnit = 2;
    XResolution = 72;
    YResolution = 72;
    "_YCbCrPositioning" = 1;
};
}

Y esto:

2012-10-12 23:17:45.421 Waypointer[3120:907] metadataAsMutable Info: {
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 1;
PixelHeight = 2448;
PixelWidth = 3264;
"{Exif}" =     {
    ApertureValue = "2.526069";
    BrightnessValue = "-4.410617";
    ColorSpace = 1;
    ComponentsConfiguration =         (
        1,
        2,
        3,
        0
    );
    ExifVersion =         (
        2,
        2,
        1
    );
    ExposureMode = 0;
    ExposureProgram = 2;
    ExposureTime = "0.06666667";
    FNumber = "2.4";
    Flash = 16;
    FlashPixVersion =         (
        1,
        0
    );
    FocalLenIn35mmFilm = 35;
    FocalLength = "4.28";
    ISOSpeedRatings =         (
        800
    );
    MeteringMode = 5;
    PixelXDimension = 3264;
    PixelYDimension = 2448;
    SceneCaptureType = 0;
    SensingMethod = 2;
    ShutterSpeedValue = "3.906905";
    SubjectArea =         (
        1631,
        1223,
        881,
        881
    );
    SubjectDistance = "69 m";
    UserComment = "[S.D.] kCGImagePropertyExifUserComment";
    WhiteBalance = 0;
};
"{GPS}" =     {
    DateStamp = "camera GPS Date Stamp";
    DestLatitude = "subject coord Latitude";
    DestLongitude = "subject coord Longitude";
    ImgDirection = "camera direction (heading) in degrees";
    Latitude = "camera coord Latitude";
    Longitude = "camera coord Longitude";
};
"{Raw}" =     {
};
"{TIFF}" =     {
    Orientation = 1;
    ResolutionUnit = 2;
    XResolution = 72;
    YResolution = 72;
    "_YCbCrPositioning" = 1;
};
}

Y, después de que todo está hecho, esto:

2012-10-12 23:17:47.131 Waypointer[3120:907] Properties {
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 1;
PixelHeight = 2448;
PixelWidth = 3264;
"{Exif}" =     {
    ApertureValue = "2.526069";
    BrightnessValue = "-4.410617";
    ColorSpace = 1;
    ComponentsConfiguration =         (
        0,
        0,
        0,
        1
    );
    ExifVersion =         (
        2,
        2,
        1
    );
    ExposureMode = 0;
    ExposureProgram = 2;
    ExposureTime = "0.06666667";
    FNumber = "2.4";
    Flash = 16;
    FlashPixVersion =         (
        1,
        0
    );
    FocalLenIn35mmFilm = 35;
    FocalLength = "4.28";
    ISOSpeedRatings =         (
        800
    );
    MeteringMode = 5;
    PixelXDimension = 3264;
    PixelYDimension = 2448;
    SceneCaptureType = 0;
    SensingMethod = 2;
    ShutterSpeedValue = "3.906905";
    SubjectArea =         (
        1631,
        1223,
        881,
        881
    );
    UserComment = "[S.D.] kCGImagePropertyExifUserComment";
    WhiteBalance = 0;
};
"{JFIF}" =     {
    DensityUnit = 1;
    JFIFVersion =         (
        1,
        1
    );
    XDensity = 72;
    YDensity = 72;
};
"{TIFF}" =     {
    Orientation = 1;
    ResolutionUnit = 2;
    XResolution = 72;
    YResolution = 72;
    "_YCbCrPositioning" = 1;
};
}

Como lo ilustra el ejemplo, puede ver los metadatos originales de la imagen, su modificación y luego su salida final.

El resultado final es lo que me molesta porque no importa lo que haga, ¡no puedo mantener mis valores modificados!

¿Hay algún formato muy específico que me falta? ¿Por qué iOS está eliminando mis modificaciones? ¿Qué necesito hacer para agregar estos valores adicionales? Se enumeran en el encabezado. Y se calcula que debe aceptarse fácilmente.