Image Annotation Plugins
Recently, a faculty member asked about installing the PRO version the plugin 'Draw Attention' (https://wordpress.org/plugins/draw-attention/) for image annotation for her art history class. The free version currently on the Commons only allows annotation on one image per site and she was hoping to use it for student assignments (30-60 images per site). The plugin does not have front-end annotation but rather requires the user to create the annotations through the dashboard area of the plugin. In the dashboard, users select the clickable areas for front-end users to explore. From what I can tell in the free version, like a post, a user chooses an image, adds content (annotations) and posts the image. Tested here: https://coursetest.commons.gc.cuny.edu/?da_image=123
The plugin is fairly easy to use through the dashboard interface but its unclear whether users can annotate images posted by others (but probably not, like posts)so its possible that this plugin does not allow for shared/collaborative annotation on a image.
Just FYI, the PRO version costs $74/year for one site and $124/year for unlimited sites, but I know the Commons tends to steer away from paid plugins. Moreover, dashboard editing and non-collaborative annotation may not be not ideal for a class setup. I think front-end annotation might work better since having users access the image through the back-end and set up annotations might be confusing for students and require admin user status as opposed to author status.
I'm not sure of other tools that do collaborative image annotation (other than VOCAT). One possibility is Demon Image Annotation but this plugin might work the same way as Draw Attention