Last weekend, I decided to expand Coverflow to work with my entire photo album. This involved exploring the MusicLibrary and PhotoLibrary frameworks to find out how I could extract a complete set of albums and their pictures. The PLPhotoLibrary class proved to hold the key. With it, I could request an album list, and then build up a dictionary of photos that linked back from the image identifier to the album it came from.

    id pl = [[PLPhotoLibrary alloc] 
       initWithPath:@"/var/mobile/Media/Photos"];
    picList = [[NSMutableDictionary alloc] init];
    int num = [[pl albums] count];

    // Add every photo in the library

    int i, j;

    for (i = 0; i < num; i++)

    {

      album = [[pl albums] objectAtIndex:i];

      id imgs = [album images];

      for (j = 0; j < [imgs count]; j++)  {

          id imgid = [NSNumber numberWithInt:

               [[imgs objectAtIndex:j] imageID]];

          [picList setObject:album forKey:imgid];

      }

    }

Once the photos were all gathered, I could then pull back out each photo's album, and request a low-quality (thus memory-saving) CGImageRef.

// Image Data Source Method

- (void) coverFlow:(id)cf requestImageAtIndex: (int)idx quality: (int)q

{

   id imgID = [[picList allKeys] objectAtIndex:idx];

   id album = [picList objectForKey:imgID];

   id img = [[album imageWithImageID:[imgID integerValue]] 

               createLowResolutionFullScreenCGImageRef];

   [cfLayer setImage:img  atIndex:idx type:q];

}

Together this allowed me to update my Coverflow sample to work with all onboard images. As you'll find when running this sample, I have not yet figured out some sort of matting scheme, so all the images are squashed (regardless of original aspect ratio) into a square.

The sample code is available as FullAlbum.m. You can also play with PhotoPhun, a simple non-coverflow application built over this library code.