来自Splitview Controller加载的图像的iOS元数据

Question

I have a SplitviewController that displays a list of images. When one is clicked it will be shown on the main screen and I want to display the metadata of this image below it. My images are managed by a self written class that stores them as UIImages. I got 4 example pictures that are just embedded as Ressource files and loaded via

NSString* pathToImageFile = [[NSBundle mainBundle] pathForResource:imageName
                                                                ofType:@"jpg"];
UIImage* img = [UIImage imageWithContentsOfFile:pathToImageFile];

The User has the option to add pictures to this list via imagePicker either out of the library or the camera.

Now I need a way to access the metadata of the images when the user chooses a row in the table. I know that UIImages don't carry any metadata, but is there a way to access the underlying jpg and retrieve metadata from there? The main problem hereby would be that I have three different sources for the images (app directoy, photo album, camera). Or do I need to rewrite my image store class that it has to keep track of my metadata or my URLs as well as the images? The following is my didSelectRow method where I want to add a method to retrieve metadata of the selected image.

- (void)tableView:(UITableView *)tableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
     UIImage *img = [[[ImageStore sharedStore] getAllImages] objectAtIndex:[indexPath row]];
     self.detailViewController.detailItem = img;
}

Thanks for your help!

Answer 1

If it's in the app directory you can read the file directly. There is code here which will get the metadata using CGImageSource .

http://blog.depicus.com/index.php/2011/05/07/getting-exif-data-from-images-on-ios/

The photo library you get using ALAssetLibrary . Eventually you will drill down to an ALAssetRepresentation , which has a metadata property.

For a camera picture, to be honest I'm not entirely sure how you can do that without writing it to disk (photo library or application directory) first.