Image Tag aims to be the image tagging solution for Drupal, providing a flexible suite of modules for "tagging" areas in an image. Other examples of this include Facebook, Flickr, iPhoto, etc.
The main Image Tag module provides a fieldable image tag entity that defines the bounding box of a tag. It will be possible to define any number of tag types with different fields. Possible examples may include: user tag, simple text annotation tag, product tag to tag multiple products in one image.