SaveImage.m

-(void)saveImage:(UIImage * _Nonnull)image metadata:(NSDictionary * _Nullable)metadata
{
#if  0	// attach only Exif
	NSDictionary *exif = metadata[@"{Exif}"];
	metadata = (exif == nil)?  nil : @{ @"{Exif}" : exif };
#endif

	NSMutableData *jpegData = [[NSMutableData alloc] init];
	CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)jpegData, kUTTypeJPEG, 0, NULL);
	CGImageDestinationAddImage(imageDestination, image.CGImage, (__bridge CFDictionaryRef)metadata);
	BOOL writeSuccess = CGImageDestinationFinalize(imageDestination);	
	CFRelease(imageDestination);
	if(!writeSuccess)
		return;

	[[PHPhotoLibrary sharedPhotoLibrary]
	 	performChanges:^{
			PHAssetCreationRequest *assetCreation = [PHAssetCreationRequest creationRequestForAsset];
			[assetCreation addResourceWithType:PHAssetResourceTypePhoto data:jpegData options:nil];
		}
		completionHandler:^(BOOL success, NSError * _Nullable error) {
			NSLog(@"%d, %@", success, error);
		}
	];
}