Write UIImage along with metadata (EXIF, GPS, TIFF) in iPhone’s Photo library

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Apple has updated their article addressing this issue (Technical Q&A QA1622). If you’re using an older version of Xcode, you may still have the article that says, more or less, tough luck, you can’t do this without low-level parsing of the image data.

https://developer.apple.com/library/ios/#qa/qa1622/_index.html

I adapted the code there as follows:

- (void) saveImage:(UIImage *)imageToSave withInfo:(NSDictionary *)info
{
    // Get the assets library
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    // Get the image metadata (EXIF & TIFF)
    NSMutableDictionary * imageMetadata = [[info objectForKey:UIImagePickerControllerMediaMetadata] mutableCopy];

    // add GPS data
    CLLocation * loc = <•••>; // need a location here
    if ( loc ) {
        [imageMetadata setObject:[self gpsDictionaryForLocation:loc] forKey:(NSString*)kCGImagePropertyGPSDictionary];
    }

    ALAssetsLibraryWriteImageCompletionBlock imageWriteCompletionBlock =
    ^(NSURL *newURL, NSError *error) {
        if (error) {
            NSLog( @"Error writing image with metadata to Photo Library: %@", error );
        } else {
            NSLog( @"Wrote image %@ with metadata %@ to Photo Library",newURL,imageMetadata);
        }
    };

    // Save the new image to the Camera Roll
    [library writeImageToSavedPhotosAlbum:[imageToSave CGImage] 
                                 metadata:imageMetadata 
                          completionBlock:imageWriteCompletionBlock];
    [imageMetadata release];
    [library release];
}

and I call this from

imagePickerController:didFinishPickingMediaWithInfo:

which is the delegate method for the image picker.

I use a helper method (adapted from GusUtils) to build a GPS metadata dictionary from a location:

- (NSDictionary *) gpsDictionaryForLocation:(CLLocation *)location
{
    CLLocationDegrees exifLatitude  = location.coordinate.latitude;
    CLLocationDegrees exifLongitude = location.coordinate.longitude;

    NSString * latRef;
    NSString * longRef;
    if (exifLatitude < 0.0) {
        exifLatitude = exifLatitude * -1.0f;
        latRef = @"S";
    } else {
        latRef = @"N";
    }

    if (exifLongitude < 0.0) {
        exifLongitude = exifLongitude * -1.0f;
        longRef = @"W";
    } else {
        longRef = @"E";
    }

    NSMutableDictionary *locDict = [[NSMutableDictionary alloc] init];

    [locDict setObject:location.timestamp forKey:(NSString*)kCGImagePropertyGPSTimeStamp];
    [locDict setObject:latRef forKey:(NSString*)kCGImagePropertyGPSLatitudeRef];
    [locDict setObject:[NSNumber numberWithFloat:exifLatitude] forKey:(NSString *)kCGImagePropertyGPSLatitude];
    [locDict setObject:longRef forKey:(NSString*)kCGImagePropertyGPSLongitudeRef];
    [locDict setObject:[NSNumber numberWithFloat:exifLongitude] forKey:(NSString *)kCGImagePropertyGPSLongitude];
    [locDict setObject:[NSNumber numberWithFloat:location.horizontalAccuracy] forKey:(NSString*)kCGImagePropertyGPSDOP];
    [locDict setObject:[NSNumber numberWithFloat:location.altitude] forKey:(NSString*)kCGImagePropertyGPSAltitude];

    return [locDict autorelease];

}

So far this is working well for me on iOS4 and iOS5 devices.

Update: and iOS6/iOS7 devices. I built a simple project using this code:

https://github.com/5teev/MetaPhotoSave

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