I am currently working with fabric.js 4.6.0 and place different fabric types on a canvas (Rect, Polygon, Polyline, ...).

Now, I want to get the percentage of the coverage of the underlying HTMLCanvasElement. Areas of fabric.js objects which are outside of the HTMLCanvasElement should be ignored.

I know, that I can use fabric.js' Canvas.toJSON() to get the data of the objects placed on the canvas, but I have no idea how to use that to calculate the coverage.

Could someone direct me to an algorithm to do that?