Best way to rebase slideshow backgrounds?

[dude-at-RA]

I'm converting markdown to revealjs html, using background-image as an attribute on headers. During the build, we also use the rebase_relative_paths extension for markdown.

It looks like rebase_relative_paths only works on images and links. Does anyone have a snazzy way to rebase the paths in attributes as well?

Currently I'm doing this with a few passes of pandoc and a few lua filters that do the following:

1. find headers with the background-image attribute at the Blocks level and add an image below with the same path (pandoc command 1)
2. run pandoc from markdown to markdown with the rebase_relative_paths extension to adjust the image paths. move the image path back to the header attribute, then remove the added image (pandoc command 2)
3. run pandoc to convert the rebased markdown to revealjs html (pandoc command 3)

This works, but I suspect there might be an easier way to do this.