Graphics application with rails and javascript

Hi all,

I’m trying to develop a video annotation application with Rails. First
things I need to do is to select a bounding box of an object in a video
frame and back it up in my database.

From now I was able to draw some bounding boxes using “javascript” and
the “canvas” elements of html5. But I can’t figure out how to link my
javascript bounding boxes to my rails active record bounding boxes.
Inversely, I’d like to draw all stored bounding boxes in the canvas.

Is there any exemple of use of graphics element in rails ? Any tips will
be helpfull.