IIOReadUpdateListener contains certain thumbnail related methods such as thumbnailUpdate, thumbnailPassStarted, thumbnailPassCompleted. These methods are never getting called when a thumbnail is read from the input source through readThumbnail() API call. All the IIOReadProgressListener methods are notified properly. This is noticed for JPG format. No other format supports thumbnails.

The thumbnailUpdate() method must be notified when a thumbnail is read and also the documentation for readThumbnail() must be updated so as to include this behaviour (IIOReadUpdateListener). Currently it involves only IIOReadProgressListener.

This is reproducible on all the platforms right from JDK1.4.

I have attached a sample testcase and a jpg image containing couple of thumbnails. Execute the test and watch the console. If you don't see any message from thumbnailUpdate() method, then the bug is reproduced.