Save exif metadata with the new PHPhotoLibrary

Question

I am currently using AVCaptureStillImageOutputto get a full resolution image. I can also get exif metadata using the following code:

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
     { 

         CFDictionaryRef metaDict = CMCopyDictionaryOfAttachments(NULL, imageSampleBuffer, kCMAttachmentMode_ShouldPropagate);
         CFMutableDictionaryRef mutableDict = CFDictionaryCreateMutableCopy(NULL, 0, metaDict);

         NSLog(@"test attachments %@", mutableDict);

         // set the dictionary back to the buffer
         CMSetAttachments(imageSampleBuffer, mutableDict, kCMAttachmentMode_ShouldPropagate);

         NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];

         UIImage *image = [[UIImage alloc] initWithData:imageData];    
         [self.delegate frameReadyToSave:image withExifAttachments: mutableDict];
     }];

Metadata is in a variable mutableDict. Now I want to save this picture in two different places, with metadata. I want to save it to disk in application folders and in the Photo Library.

Now I tried to save the image in another method using the following (the image variable you see is a custom object):

NSData* imageData = UIImageJPEGRepresentation(image.image, 1.0f);

[imageData writeToFile:image.filePath atomically:YES];

UIImageWriteToSavedPhotosAlbum(image.image, nil, nil, nil);

Now the image is correctly saved, but does not contain Exif metadata.

From what I read, I need to use PHPhotoLibrary to do this, but the documentation is not too talkative. Here is what I found:

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    PHAssetChangeRequest *createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image.image];      

} completionHandler:nil];

?

Answer 1

ImageIO, :

-(void)frameReadyToSave:(UIImage*)image withExifAttachments:(NSMutableDictionary*)mutableDict
{
    NSData* imageData = UIImageJPEGRepresentation(image, 1.0f);
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef) imageData, NULL);
    __block NSURL* tmpURL = [NSURL fileURLWithPath:@"example.jpg"]; //modify to your needs
    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef) tmpURL, kUTTypeJPEG, 1, NULL);
    CGImageDestinationAddImageFromSource(destination, source, 0, (__bridge CFDictionaryRef) mutableDict);
    CGImageDestinationFinalize(destination);
    CFRelease(source);
    CFRelease(destination);
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:tmpURL];
    }   completionHandler:^(BOOL success, NSError *error) {
        //cleanup the tmp file after import, if needed
    }];
}