Ios CFDictionary更新到PHPhotoLibrary kCGImagePropertyExifDictionary不接受

在iOS 8.4照片集合中将图像资源添加到相册时，我正在尝试添加/修改图像元数据。下面的代码成功地添加了GPS字典，但没有添加或更改EXIF数据（我已经检查了图像标题并使用EXIF工具进行确认）。我尝试了两种不同的方法（请参见altSetMyImageInfo），但结果相同。我错过了什么

 @property (nonatomic) CLLocation *location; 
. . .
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:^( CMSampleBufferRef imageDataSampleBuffer, NSError *error ) {
    if ( imageDataSampleBuffer ) {
        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
        CFDictionaryRef tempDict = CMCopyDictionaryOfAttachments(NULL, imageDataSampleBuffer, kCMAttachmentMode_ShouldPropagate);
        CFMutableDictionaryRef theDict = CFDictionaryCreateMutableCopy(NULL, 0, tempDict);

        [self setMyImageInfo:theDict];
        [self setMyLocation:theDict];

        CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
        CFStringRef UTI = CGImageSourceGetType(source);                 
        NSMutableData *newImageData = [NSMutableData data];
        CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)newImageData,UTI,1,NULL);
        BOOL success = CGImageDestinationFinalize(destination);
        CFRelease(destination);
        CFRelease(source);
    }
}
. . .
if ( [PHAssetResourceCreationOptions class] ) {
    [[PHAssetCreationRequest creationRequestForAsset] addResourceWithType:PHAssetResourceTypeFullSizePhoto data:newImageData options:nil]; 
}
else {
     NSError *error = nil;
     [newImageData writeToURL:temporaryFileURL options:NSDataWritingAtomic error:&error];
     if ( error ) {
        NSLog( @"Error: %@", error );
     }
     else {
          PHAssetChangeRequest *newImageRequest = [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:temporaryFileURL];
          PHAssetCollectionChangeRequest *albumChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:theAlbum];
          [albumChangeRequest addAssets:@[newImageRequest.placeholderForCreatedAsset]];
}
. . .             
- (void) setMyImageInfo:(CFMutableDictionaryRef)theDict
{
NSMutableDictionary *exif = [NSMutableDictionary dictionary];
[exif setObject:@"2.2.2" forKey:(NSString *)kCGImagePropertyExifVersion];
[exif setObject:@“MyIdentity” forKey:(NSString *)kCGImagePropertyExifImageUniqueID];
[exif setObject:@"I hope this works!" forKey:(NSString *)kCGImagePropertyExifUserComment];

CFDictionarySetValue(theDict, kCGImagePropertyExifDictionary, (__bridge void *)exif);    
}
- (void) setMyLocation:(CFMutableDictionaryRef)theDict
{
NSMutableDictionary *gps = [NSMutableDictionary dictionary];
[gps setObject:@"2.2.0.0" forKey:(NSString *)kCGImagePropertyGPSVersion];
NSDateFormatter *formatter  = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"HH:mm:ss.SSSSSS"];
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
[gps setObject:[formatter stringFromDate:self.location.timestamp] forKey:(NSString *)kCGImagePropertyGPSTimeStamp];
[formatter setDateFormat:@"yyyy:MM:dd"];
[gps setObject:[formatter stringFromDate:self.location.timestamp] forKey:(NSString *)kCGImagePropertyGPSDateStamp];
CGFloat latitude = self.location.coordinate.latitude;
if (latitude < 0) {
    latitude = -latitude;
    [gps setObject:@"S" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef];
} else {
    [gps setObject:@"N" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef];
}
[gps setObject:[NSNumber numberWithFloat:latitude] forKey:(NSString *)kCGImagePropertyGPSLatitude];
CGFloat longitude = self.location.coordinate.longitude;
if (longitude < 0) {
    longitude = -longitude;
    [gps setObject:@"W" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef];
} else {
    [gps setObject:@"E" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef];
}
[gps setObject:[NSNumber numberWithFloat:longitude] forKey:(NSString *)kCGImagePropertyGPSLongitude]; 
CGFloat altitude = self.location.altitude;
if (!isnan(altitude)){
    if (altitude < 0) {
        altitude = -altitude;
        [gps setObject:@"1" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef];
    } else {
        [gps setObject:@"0" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef];
    }
    [gps setObject:[NSNumber numberWithFloat:altitude] forKey:(NSString *)kCGImagePropertyGPSAltitude];
}    
if (self.location.speed >= 0){
    [gps setObject:@"K" forKey:(NSString *)kCGImagePropertyGPSSpeedRef];
    [gps setObject:[NSNumber numberWithFloat:self.location.speed*3.6] forKey:(NSString *)kCGImagePropertyGPSSpeed];
}
if (self.location.course >= 0){
    [gps setObject:@"T" forKey:(NSString *)kCGImagePropertyGPSTrackRef];
    [gps setObject:[NSNumber numberWithFloat:self.location.course] forKey:(NSString *)kCGImagePropertyGPSTrack];
}
CFDictionarySetValue(theDict, kCGImagePropertyGPSDictionary, (__bridge void *)gps);
}

- (void) altSetMyImageInfo:(CFMutableDictionaryRef)theDict
{
CFStringRef imageUniqueID = CFStringCreateWithCString(NULL, [@“MyImageID” cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
CFDictionarySetValue(theDict, kCGImagePropertyExifImageUniqueID, imageUniqueID);
CFRelease (imageUniqueID);    
CFStringRef userComment = CFStringCreateWithCString(NULL, [@"I hope this works!" cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
CFDictionarySetValue(theDict, kCGImagePropertyExifUserComment, userComment);
CFRelease (userComment);
}

@property（非原子）CLLocation*location；
. . .
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:连接完成处理程序：^（CMSampleBufferRef imageDataSampleBuffer，NSError*错误）{
if（imageDataSampleBuffer）{
NSData*imageData=[AVCaptureSillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer]；
CFDictionaryRef tempDict=cmCopyDictionaryOfTachments（NULL，imageDataSampleBuffer，kCMAttachmentMode_ShouldPropagate）；
CFMutableDictionaryRef theDict=CFDictionaryCreateMutableCopy（NULL，0，tempDict）；
[自我设置MyImageInfo:theDict]；
[自我设置位置：theDict]；
CGImageSourceRef source=CGImageSourceCreateWithData（（uu桥CFDataRef）imageData，NULL）；
CFStringRef UTI=CGImageSourceGetType（源）；
NSMutableData*newImageData=[NSMutableData]；
CGImageDestinationRef destination=CGImageDestinationCreateWithData（（uu桥CFMutableDataRef）newImageData，UTI，1，NULL）；
BOOL success=CGImageDestinationFinalize（目的地）；
目的地；
CFRelease（来源）；
}
}
. . .
if（[PHAssetResourceCreationOptions类]）{
[[PhasSetCreationRequestCreationRequestForAsset]添加ResourceWithType:PHAssetResourceTypeFullSizePhoto数据：新图像数据选项：nil]；
}
否则{
n错误*错误=nil；
[newImageData writeToURL:temporaryFileURL选项：NSDataWritingAtomic错误：&错误]；
如果（错误）{
NSLog（@“错误：%@”，错误）；
}
否则{
PHAssetChangeRequest*newImageRequest=[PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:temporaryFileURL]；
PHAssetCollectionChangeRequest*albumChangeRequest=[PhasSetCollectionChangeRequestChangeRequestforAssetCollection:theAlbum]；
[AlbumChangeRequestAddAssets:@[newImageRequest.placeholderForCreatedAsset]]；
}
. . .             
-（void）设置MyImageInfo:（CFMutableDictionaryRef）ICT
{
NSMutableDictionary*exif=[NSMutableDictionary]；
[exif setObject:@“2.2.2”forKey:（NSString*）kCGImagePropertyExifVersion]；
[exif setObject:@“MyIdentity”forKey:（NSString*）kCGImagePropertyExifImageUniqueID]；
[exif setObject:@“我希望这能起作用！”forKey:（NSString*）kCGImagePropertyExifUserComment]；
CFDICTORYSETVALUE（信息技术、KCGIMAGEPROPERTYYEXIFDICTORY，（u桥无效*）exif）；
}
-（void）setMyLocation:（CFMutableDictionaryRef）ICT
{
NSMutableDictionary*gps=[NSMutableDictionary]；
[gps setObject:@“2.2.0.0”forKey:（NSString*）KCGimagePropertyGPVersion]；
NSDateFormatter*格式化程序=[[NSDateFormatter alloc]init]；
[格式化程序setDateFormat:@“HH:mm:ss.ssss”]；
[格式化程序设置时区：[N时区时区修订：@“UTC”]；
[gps setObject:[formatter stringFromDate:self.location.timestamp]forKey:（NSString*）KCGimagePropertyGPTimeStamp]；
[格式化程序setDateFormat:@“yyyy:MM:dd”]；
[gps setObject:[formatter stringFromDate:self.location.timestamp]forKey:（NSString*）kCGImagePropertyGPSDateStamp]；
CGFloat LATIONE=self.location.coordinate.latitude；
如果（纬度<0）{
纬度=-纬度；
[gps设置对象：@“S”forKey:（NSString*）kCGImagePropertyGPSLatitudeRef]；
}否则{
[gps设置对象：@“N”forKey:（NSString*）kCGImagePropertyGPSLatitudeRef]；
}
[gps设置对象：[NSNumber numberWithFloat:latitude]forKey:（NSString*）kCGImagePropertyGPSLatitude]；
CGFloat经度=self.location.coordinate.longitude；
如果（经度<0）{
经度=-经度；
[gps设置对象：@“W”forKey:（NSString*）kCGImagePropertyGPSLongitudeRef]；
}否则{
[gps设置对象：@“E”forKey:（NSString*）kCGImagePropertyGPSLongitudeRef]；
}
[gps设置对象：[NSNumber numberWithFloat:longitude]forKey:（NSString*）kCGImagePropertyGPSLongitude]；
CGFloat高度=自身位置高度；
如果（！isnan（高度））{
如果（高度<0）{
高度=-高度；
[gps设置对象：@“1”forKey:（NSString*）kCGImagePropertyGPSAltitudeRef]；
}否则{
[gps设置对象：@“0”forKey:（NSString*）kCGImagePropertyGPSAltitudeRef]；
}
[gps设置对象：[NSNumber numberWithFloat:altitude]forKey:（NSString*）KCGimagePropertyGPsaltude]；
}    
如果（self.location.speed>=0）{
[gps设置对象：@“K”forKey:（NSString*）kCGImagePropertyGPSSpeedRef]；
[gps设置对象：[NSNumber numberWithFloat:self.location.speed*3.6]forKey:（NSString*）KCGimagePropertyGPSpeed]；
}
如果（self.location.course>=0）{
[gps设置对象：@“T”forKey:（NSString*）kCGImagePropertyGPSTrackRef]；
[gps设置对象：[NSNumber numberWithFloat:self.location.course]forKey:（NSString*）kCGImagePropertyGPSTrack]；
}
CFDictionarySetValue（ICT、KCGimagePropertyGPS字典、（\u桥空*）gps）；
}
-（void）altSetMyImageInfo:（CFMutableDictionaryRef）ICT
{
CFStringRef imageUniqueID=CFStringCreateWithCString（NULL，[@“MyImageID”cStringUsingEncoding:NSASCIIStringEncoding]，kCFStringEncodingASCII）；
CFDictionarySetValue（ICT、kCGImagePropertyExifImageUniqueID、imageUniqueID）；
CFRelease（imageUniqueID）；
CFStringRef userComment=CFStringCreateWithCString（NULL，[@“我希望这能起作用！”cStringUsingEncoding:NSASCIIStringEncoding]，kcfStringCodingAscii）；
CFDictionarySetValue（ICT、kCGImagePropertyExifUserComment、userComment）；
CFRelease（userComment）；
}

这个问题的答案涉及很多事情。缺少一个小例子“CGImageSourceRef source”。最重要的是，由于

@import CoreLocation; // MAS: for GPS (line 11)
@property (strong, nonatomic) CLLocationManager *locationManager;  // MAS: for image metadata (line 42)
@property (nonatomic) CLLocation *location; //  MAS: get it early and save it here (line 43)
@property (assign, nonatomic) id< CLLocationManagerDelegate > delegate; // MAS: do we really need this? (line 44)
/* MAS: Instantiate location manager (in viewDidLoad, about line 70)
 */
 self.locationManager = [[CLLocationManager alloc] init];
/* MAS: end
 */
    [self startStandardUpdates];  // MAS: get our location (in viewDidLoad about line 201, not quite at the end)
/* MAS: (still in veiwDidLoad about line 206 after dispatch)
 */
if ([CLLocationManager locationServicesEnabled]) {
    NSLog(@"location services enabled");
}
else {
    NSLog( @"Could not add location services to the session" );
    // self.setupResult = PikBitSetupResultSessionConfigurationFailed;
    // Display alert to the user.
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Location services"
                                                                   message:@"Location services are not enabled on this device. Please enable location services in settings."
                                                            preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"Dismiss" style:UIAlertActionStyleDefault
                                                          handler:^(UIAlertAction * action) {}]; // NULL action to dismiss the alert.
    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];
}

if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusNotDetermined)
{
    [self.locationManager requestWhenInUseAuthorization];
    NSLog(@"location authorization status not determined");

} else if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusDenied) {
    NSLog(@"location services authorization was previously denied by the user.");
    // Display alert to the user.
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Location services"
                                                                   message:@"Location services were previously denied by the user. Please enable location services for this app in settings."
                                                            preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"Dismiss" style:UIAlertActionStyleDefault
                                                          handler:^(UIAlertAction * action) {}]; // Do nothing action to dismiss the alert.
    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];
}

/* MAS: end
 */
            /* MAS: about line 616, once you have image NSData
             */
            CFDictionaryRef tempDict = CMCopyDictionaryOfAttachments(NULL, imageDataSampleBuffer, kCMAttachmentMode_ShouldPropagate);
            CFMutableDictionaryRef theDict = CFDictionaryCreateMutableCopy(NULL, 0, tempDict);

            [self setMyImageInfo:theDict];
            [self setMyLocation:theDict];

            CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
            CFStringRef UTI = CGImageSourceGetType(source);
            NSMutableData *newImageData = [NSMutableData data];
            CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)newImageData,UTI,1,NULL);
            if(!destination) {
                NSLog(@"***Could not create image destination ***");
            }
            CGImageDestinationAddImageFromSource(destination,source,0, (CFDictionaryRef) theDict);

            BOOL success = CGImageDestinationFinalize(destination);
            CFRelease(destination);
            CFRelease(source);
            if( success ) {
                NSLog(@"it worked, let's see the metadata");
                [self checkEXIF:newImageData];
            }
            else {
                NSLog(@"***Could not create data from image destination ***");
            }
            /* MAS: end
             */
[[PHAssetCreationRequest creationRequestForAsset] addResourceWithType:PHAssetResourceTypePhoto data:newImageData options:nil]; // MAS: change data to 'NewImageData' (about line 654)
                            [newImageData writeToURL:temporaryFileURL options:NSDataWritingAtomic error:&error]; // MAS: change source to newImageData (about line 668)
/* MAS: start (immediately before @end)
 */
#pragma mark - location delegate methods

// Start the standard location service

- (void)startStandardUpdates
{
// set the delegate and the parameters
self.locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;

// Set a movement threshold for new events.
self.locationManager.distanceFilter = 500; // meters

[self.locationManager startUpdatingLocation];
NSLog(@"location manager started");
}

// Delegate methods

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
// If it's a relatively recent event, turn off updates to save power.
self.location = [locations lastObject];
NSLog(@"location manager delegate used");
NSDate* eventDate = self.location.timestamp;
NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
if (fabs(howRecent) < 15.0) {
    // If the event is recent, do something with it.
    NSLog(@"latitude %+.6f, longitude %+.6f\n",
          self.location.coordinate.latitude,
          self.location.coordinate.longitude);
}
else {
    NSLog(@"latitude %+.6f, longitude %+.6f\n",
          self.location.coordinate.latitude,
          self.location.coordinate.longitude);

}
/*  MAS: for optimizing usage (later)

 [manager stopUpdatingLocation]; // If we only want one update.

 manager.delegate = nil;         // We might be called again here, even though we
 // called "stopUpdatingLocation", so remove us as the delegate to be sure.
 */
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
// report any errors returned back from Location Services
NSLog(@"location manager error - %@", error.description);
}

- (void) setMyImageInfo:(CFMutableDictionaryRef)theDict
{
NSString *temp = @"This is a very long string, used to test the loading of the image description field";
NSString *tempID = @"ABCDEFGHIJKLMNOPQRSTUVWXYZ012345"; // used to test imageUniqueID field, should the 33rd character be a nul?

//
if (theDict) {
    // save a dictionary of the TIFF image properties
    CFDictionaryRef tiffData = CFDictionaryGetValue(theDict, kCGImagePropertyTIFFDictionary);

    CFMutableDictionaryRef tiffDataMut;
    if (tiffData) {
        tiffDataMut = CFDictionaryCreateMutableCopy(nil, 0, tiffData);
    }
    else {
        tiffDataMut = CFDictionaryCreateMutable(nil, 0,
                                                &kCFTypeDictionaryKeyCallBacks,  &kCFTypeDictionaryValueCallBacks);
    }
    // The best place to store a long string --
    CFStringRef imageDescription = CFStringCreateWithCString(NULL, [temp cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(tiffDataMut, kCGImagePropertyTIFFImageDescription, imageDescription);
    CFRelease (imageDescription);
    // Carry the brand into the image --
    CFStringRef software = CFStringCreateWithCString(NULL, [@"MyApp" cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(tiffDataMut, kCGImagePropertyTIFFSoftware, software);
    CFRelease (software);
    // Carry the manufacturer into the image --
    CFStringRef make = CFStringCreateWithCString(NULL, [@"Apple" cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(tiffDataMut, kCGImagePropertyTIFFMake, make);
    CFRelease (make);
    // Carry the device name into the image --
    CFStringRef model = CFStringCreateWithCString(NULL, [@"iPhone" cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(tiffDataMut, kCGImagePropertyTIFFModel, model);
    CFRelease (model);

    CFDictionarySetValue(theDict, kCGImagePropertyTIFFDictionary, tiffDataMut);

    CFRelease(tiffDataMut);

    // Now do the same for EXIF
    // save a dictionary of the EXIF image properties
    CFDictionaryRef exifData = CFDictionaryGetValue(theDict, kCGImagePropertyExifDictionary);

    CFMutableDictionaryRef exifDataMut;
    if (exifData) {
        exifDataMut = CFDictionaryCreateMutableCopy(nil, 0, exifData);
    }
    else {
        exifDataMut = CFDictionaryCreateMutable(nil, 0,
                                                &kCFTypeDictionaryKeyCallBacks,  &kCFTypeDictionaryValueCallBacks);
    }
    // This is a good place to store an ID, but it only holds 33 characters --
    CFStringRef imageUniqueID = CFStringCreateWithCString(NULL, [tempID cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(exifDataMut, kCGImagePropertyExifImageUniqueID, imageUniqueID);
    CFRelease (imageUniqueID);
    // Just to see that it works --
    CFStringRef userComment = CFStringCreateWithCString(NULL, [@"I hope this works!  And it does!!" cStringUsingEncoding:NSASCIIStringEncoding], kCFStringEncodingASCII);
    CFDictionarySetValue(exifDataMut, kCGImagePropertyExifUserComment, userComment);
    CFRelease (userComment);

    CFDictionarySetValue(theDict, kCGImagePropertyExifDictionary, exifDataMut);

    CFRelease(exifDataMut);

}
else {
    NSLog(@"Metadata Dictionairy for image empty");
}

/*  alternative version (this has been tested and works) --
 // Create dictionaries -
 NSMutableDictionary *exif = [NSMutableDictionary dictionary];
 NSMutableDictionary *tiff = [NSMutableDictionary dictionary];
 // load some TIFF and EXIF data --
 [tiff setObject:temp forKey:(NSString *)kCGImagePropertyTIFFImageDescription];
 [tiff setObject:@"Apple" forKey:(NSString *)kCGImagePropertyTIFFMake];
 [tiff setObject:@"iPhone" forKey:(NSString *)kCGImagePropertyTIFFModel];
 [tiff setObject:@"PikLips" forKey:(NSString *)kCGImagePropertyTIFFSoftware];
 [exif setObject:@"I hope this works!  And it does, too!!" forKey:(NSString *)kCGImagePropertyExifUserComment];
 [exif setObject:tempID forKey:(NSString *)kCGImagePropertyExifImageUniqueID];

 // load the info into the passed CFMutableDictionaryRef --
 CFDictionarySetValue(theDict, kCGImagePropertyExifDictionary, (__bridge void *)exif);
 CFDictionarySetValue(theDict, kCGImagePropertyTIFFDictionary, (__bridge void *)tiff);

 * end
 */
}
- (void) setMyLocation:(CFMutableDictionaryRef)theDict
{
NSMutableDictionary *gps = [NSMutableDictionary dictionary];
[gps setObject:@"2.2.0.0" forKey:(NSString *)kCGImagePropertyGPSVersion];
NSDateFormatter *formatter  = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"HH:mm:ss.SSSSSS"];
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
[gps setObject:[formatter stringFromDate:self.location.timestamp] forKey:(NSString *)kCGImagePropertyGPSTimeStamp];
[formatter setDateFormat:@"yyyy:MM:dd"];
[gps setObject:[formatter stringFromDate:self.location.timestamp] forKey:(NSString *)kCGImagePropertyGPSDateStamp];
CGFloat latitude = self.location.coordinate.latitude;
if (latitude < 0) {
    latitude = -latitude;
    [gps setObject:@"S" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef];
} else {
    [gps setObject:@"N" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef];
}
[gps setObject:[NSNumber numberWithFloat:latitude] forKey:(NSString *)kCGImagePropertyGPSLatitude];
CGFloat longitude = self.location.coordinate.longitude;
if (longitude < 0) {
    longitude = -longitude;
    [gps setObject:@"W" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef];
} else {
    [gps setObject:@"E" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef];
}
[gps setObject:[NSNumber numberWithFloat:longitude] forKey:(NSString *)kCGImagePropertyGPSLongitude];
CGFloat altitude = self.location.altitude;
if (!isnan(altitude)){
    if (altitude < 0) {
        altitude = -altitude;
        [gps setObject:@"1" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef];
    } else {
        [gps setObject:@"0" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef];
    }
    [gps setObject:[NSNumber numberWithFloat:altitude] forKey:(NSString *)kCGImagePropertyGPSAltitude];
}
if (self.location.speed >= 0){
    [gps setObject:@"K" forKey:(NSString *)kCGImagePropertyGPSSpeedRef];
    [gps setObject:[NSNumber numberWithFloat:self.location.speed*3.6] forKey:(NSString *)kCGImagePropertyGPSSpeed];
}
if (self.location.course >= 0){
    [gps setObject:@"T" forKey:(NSString *)kCGImagePropertyGPSTrackRef];
    [gps setObject:[NSNumber numberWithFloat:self.location.course] forKey:(NSString *)kCGImagePropertyGPSTrack];
}
CFDictionarySetValue(theDict, kCGImagePropertyGPSDictionary, (__bridge void *)gps);
}
#pragma mark debug

// This is used to verify the metadata loading

- (void)checkEXIF:(NSData *) imageData {
CGImageSourceRef myImageSource = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);

CFDictionaryRef imagePropertiesDictionary;
CFDictionaryRef tiffPropertiesDictionary;
CFDictionaryRef exifPropertiesDictionary;
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                         [NSNumber numberWithBool:NO], (NSString *)kCGImageSourceShouldCache,
                         nil];

imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(myImageSource,0, (CFDictionaryRef)options);

/*  these value are produced by the system
 */
CFNumberRef imageWidth = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelWidth);
CFNumberRef imageHeight = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelHeight);

int w = 0;
int h = 0;

CFNumberGetValue(imageWidth, kCFNumberIntType, &w);
CFNumberGetValue(imageHeight, kCFNumberIntType, &h);
// NSDictionary *propertiesDict = (NSDictionary *)CFBridgingRelease(imagePropertiesDictionary); // this assignment throws an exception later in the code

NSLog(@"Image Width: %d",w);
NSLog(@"Image Height: %d",h);
// NSLog(@"Image Properties: %@", propertiesDict);

/* These values are what we added --
 */
tiffPropertiesDictionary = CFDictionaryGetValue(imagePropertiesDictionary,kCGImagePropertyTIFFDictionary);

if ( tiffPropertiesDictionary ) {
    NSString *make = (NSString *)CFDictionaryGetValue(tiffPropertiesDictionary, kCGImagePropertyTIFFMake);
    NSString *model = (NSString *)CFDictionaryGetValue(tiffPropertiesDictionary, kCGImagePropertyTIFFModel);
    NSString *imageDescription = (NSString *)CFDictionaryGetValue(tiffPropertiesDictionary, kCGImagePropertyTIFFImageDescription);
    NSString *software = (NSString *)CFDictionaryGetValue(tiffPropertiesDictionary, kCGImagePropertyTIFFSoftware);

    NSLog(@"Image Description: %@", imageDescription);
    NSLog(@"Make: %@", make);
    NSLog(@"Model: %@", model);
    NSLog(@"Software: %@", software);

}
else {
    NSLog(@"No TIFF dictionary");
}

exifPropertiesDictionary = CFDictionaryGetValue(imagePropertiesDictionary,kCGImagePropertyExifDictionary);

if ( exifPropertiesDictionary ) {
    NSString *uniqueID = (__bridge NSString *)CFDictionaryGetValue(exifPropertiesDictionary, kCGImagePropertyExifImageUniqueID);
    NSString *userComment = (__bridge NSString *)CFDictionaryGetValue(exifPropertiesDictionary, kCGImagePropertyExifUserComment);

    NSLog(@"Unique ID: %@", uniqueID);
    NSLog(@"User comment: %@", userComment);
}
else {
    NSLog(@"No EXIF dictionary");
}

CFRelease(imagePropertiesDictionary);

}

/* MAS: end
 */