How to compare coworker productivity through gitlab contribution calendars

How can I capture in a single place all gitlab user’s contribution heat maps (calendars) for easy comparison?

I suppose I could try to build up this calendar myself by fetching all repos and doing the calculations myself, especially if I want to go back more than 12 months—but that could be a lot of work!

It sure would be nice if there were a way to do this out of the box. Otherwise, a web scripting solution would work, though it is complicated by the fact that it is done as an svg and not html elements.