Access metadata (exif tags) of image taken by UIImagePickerController - iOS/iPhone

6
votes

Is it possible to access the metadata of an image captured by UIImagePickerController in iOS? I understand this can be done with AssetLibrary framework for images captured by the camera application (or otherwise present in the iPhone photo library), but can a developer access any of the metadata/exif info from within an application right after a user has taken a picture? I'm looking for any type of camera exposure-level info from an image after it has been taken. Thanks!

2
iphoneiosuiimagepickercontrollerexif
Exif is a piece of tiff-formatted data contained inside a JPEG marker. So if you have access to the raw image file, you can parse it and read it. – user180326

2 Answers

5
votes

Apparently, you can access the metadata of an image right after it has been taken. The protocol method that is called by the system after an image has been selected is:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info

The NSDictionary argument, info, contains a key: UIImagePickerControllerMediaMetadata

Now if I can figure out how to get the exif tags or any exposure-level information from this to infer basic information about light-level I will be happy. :)

0
votes

updated to iOS 11 with photos framework

Objective - C:

#import <Photos/Photos.h>

- (void)imagePickerController:(UIImagePickerController *)imagePicker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info {

    PHAsset* asset = info[UIImagePickerControllerPHAsset];

    [asset requestContentEditingInputWithOptions:nil completionHandler:^(PHContentEditingInput *contentEditingInput, NSDictionary *info) {
        CIImage *fullImage = [CIImage imageWithContentsOfURL:contentEditingInput.fullSizeImageURL];

        NSLog(@"%@", fullImage.properties.description);
    }];

    [imagePicker dismissViewControllerAnimated:YES completion:nil];
}

You also need the permission of Photo library Usage (NSPhotoLibraryUsageDescription) and then can add the following code to view did load or view did appear

[PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
    switch (status) {
        case PHAuthorizationStatusAuthorized:
            NSLog(@"PHAuthorizationStatusAuthorized");
            break;
        case PHAuthorizationStatusDenied:
            NSLog(@"PHAuthorizationStatusDenied");
            break;
        case PHAuthorizationStatusNotDetermined:
            NSLog(@"PHAuthorizationStatusNotDetermined");
            break;
        case PHAuthorizationStatusRestricted:
            NSLog(@"PHAuthorizationStatusRestricted");
            break;
    }
}];