How to edit Image metadata in iOS? - ios

Question

I am using following code to modify the metadata of Gallery Image.
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)mediaInfo
{
ALAssetsLibrary *library =nil;
void (^ALAssetsLibraryAssetForURLResultBlock)(ALAsset *) = ^(ALAsset *asset)
{
NSDictionary *metadata = asset.defaultRepresentation.metadata;
NSLog(#"Image Meta Data: %#",metadata);
NSMutableDictionary* dict=[[NSMutableDictionary alloc] initWithDictionary:metadata];
[dict setValue:#"sdfdfsfsfsfdsfsf" forKey:(NSString*)kCGImagePropertyIPTCKeywords];
UIImage *anImage = [mediaInfo valueForKey:UIImagePickerControllerOriginalImage];
NSData *imageData = UIImageJPEGRepresentation(anImage, 1.0);
[asset writeModifiedImageDataToSavedPhotosAlbum:imageData metadata:dict completionBlock:^(NSURL *assetURL, NSError *error) {
}];
};
NSURL *assetURL = [mediaInfo objectForKey:UIImagePickerControllerReferenceURL];
library = [[ALAssetsLibrary alloc] init];
[library assetForURL:assetURL
resultBlock:ALAssetsLibraryAssetForURLResultBlock
failureBlock:^(NSError *error) {
}];
}
But it is not working. Please help.

Answer 1

Here is a minimal example to do it:
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage *imageToSave = (UIImage *) [info objectForKey:UIImagePickerControllerOriginalImage];
/* modify metadata dict */
NSMutableDictionary *imageMetadata = [[info objectForKey: UIImagePickerControllerMediaMetadata] mutableCopy];
NSLog(#"Inspect current metadata: %#", imageMetadata);
NSDictionary *iptc = #{(id)kCGImagePropertyIPTCKeywords: #"awesome photo"};
[imageMetadata setObject:iptc forKey:(id)kCGImagePropertyIPTCDictionary];
/* Save to the Camera Roll with modified medatadata */
[[ALAssetsLibrary new] writeImageToSavedPhotosAlbum:imageToSave.CGImage
metadata:imageMetadata
completionBlock:NULL];
[self performDismiss];
}
If you use a metadata viewer (OS X's Preview is good enough) you'll see something like this:
But, as pawan suggests, use an existing library to do it more easily. Google around, there are quite a few options out there.