The JS/jquery library of interest is Method-Draw ([url removed, login to view]).
Method-draw is a fork of svg-edit ([url removed, login to view]), but simplified and with another frontend.
For svg-edit, there already exists the gem sketchily (([url removed, login to view])) that does exactly what is needed here.
So basically, this job consists of adapting the sketchily rails gem to work with the method-draw library.
Follow up jobs are likely if this work is done well.
This would be very quick to do. adapting the existing gem would be quick and easy, 2 days is a very conservative estimate, but I always like to estimate higher in case there are some unforseen circumstances.