Saving an html object to firebase

I'm working in ember.js my project has an image cropping mechanic. This returns to me by default a canvas object and some data necessary to redraw the cropped image.

But when I try to save the canvas object to firebase it saves it as something like [htmlObject Canvas] or something like that, so when I try to get the record and display the canvas it displays that instead of the actual canvas object.

How can I save a canvas object to firebase to use later as an actual canvas.