Problem in writing metadata to image

Question

I am using AvFoundation to take still image and adding gps info to metadata and saving to a photo album using Asset library but gps info is not saving at all.

here

Answer 1

I had exactly the same problem. I think the documentation on this topic isn't great, so I solved it in the end by looking at the metadata of a photo taken by the Camera app and trying to replicate it.

Here's a run down of the properties the Camera app saves:

• kCGImagePropertyGPSLatitude (NSNumber) (Latitude in decimal format)
• kCGImagePropertyGPSLongitude (NSNumber) (Longitude in decimal format)
• kCGImagePropertyGPSLatitudeRef (NSString) (Either N or S)
• kCGImagePropertyGPSLongitudeRef (NSString) (Either E or W)
• kCGImagePropertyGPSTimeStamp (NSString) (Of the format 04:30:51.71 (UTC timestamp))

If you stick to these you should be fine. Here's a sample:

CFDictionaryRef metaDict = CMCopyDictionaryOfAttachments(NULL, imageDataSampleBuffer, kCMAttachmentMode_ShouldPropagate);
CFMutableDictionaryRef mutable = CFDictionaryCreateMutableCopy(NULL, 0, metaDict);

NSDictionary *gpsDict = [NSDictionary 
  dictionaryWithObjectsAndKeys:
  [NSNumber numberWithFloat:self.currentLocation.coordinate.latitude], kCGImagePropertyGPSLatitude,
  @"N", kCGImagePropertyGPSLatitudeRef,
  [NSNumber numberWithFloat:self.currentLocation.coordinate.longitude], kCGImagePropertyGPSLongitude,
  @"E", kCGImagePropertyGPSLongitudeRef,
  @"04:30:51.71", kCGImagePropertyGPSTimeStamp,
  nil];

CFDictionarySetValue(mutable, kCGImagePropertyGPSDictionary, gpsDict);

//  Get the image
NSData *imageData = [AVCaptureStillImageOutput  jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];

//  Get the assets library
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library writeImageToSavedPhotosAlbum:[image CGImage] metadata:mutable completionBlock:captureComplete];

This is all in the completionHandler of the captureStillImageAsynchronouslyFromConnection method of your AVCaptureConnection object, and self.currentLocation is just a CLLocation. I hardcoded the timestamp and Lat/Lng Refs for the example to keep things simple.

Hope this helps!