Can I use javascript libraries/plugins to create heatmap without a "map" in the background?

Question

I am currently working on a web-based project that aims to visualize eye-tracking data. I want to create a heatmap (like in the figure 1) using javascript but I want to put my heatmap as a layer on an another image instead of an actual map. I have been searching some of the libraries/plugins on the internet and found some stuff like Leaflet, heatmap.js, D3.js, etc... However, I have noticed that they generally use an actual map for the background and longitude/latitude variables for the coordinates. I would be glad if you could show me if there is a way to do it without an actual map. The data will be provided before the visualization (x-y coordinates, durations of fixations)

Heatmap for eye-tracking