From the announcement:
Annotations are an important part of what authors do with Scalar, and indeed, an important part of the platform’s overall feature set…But until now, Scalar users creating image annotations have been required to manually set their coordinates, width and height. Not anymore! We’ve just finished integrating the open source plugin, Annotorious into our image annotation editor.
Read more: Alliance for Networking Visual Culture » Image Annotations Just Got Easier!.