Nice... a few years ago I worked on a project that needed overlays on a scanned image. There was a huge effort to edit images via server-client calls. I didn't like the approach and when I had some time was able to replace this with SVG in about a day. The scaling to fit the viewport was effectively "free" and so much easier in the end.
This was a React front end, and can't speak highly enough of how well it works with relatively simple dynamic svg rendering.
That whole site is a interesting read.