Quantizes (reduces color count) and traces outlines or centerlines, into a new image. Optionally creates paths for the outlines or centerlines. Also can be used to generate an SVG file for an image.
Calls autotrace (a separate program that must also be installed) to do the tracing (to SVG, a vector file format) and then imports the SVG back into Gimp.
Writing the plugin was an exploration. I explored why tracing to SVG was in programs like Inkscape but not in Gimp. I explored simplifying the daunting interface to autotrace. I explored whether tracing was useful in Gimp I found that tracing to SVG and back is not very useful in Gimp. The main problem is that it often leaves gaps between regions of color (transparent regions between colored regions.) Probably that problem could be solved. Another problem is that the underlying trace engine, autotrace, does a poor job of tracing black and white, for examples fonts. Another problem is that the SVG files are not any smaller than bitmap formats (although they will scale better.) Another problem is that importing trace paths might not be useful, especially in light of the gaps between colored regions.
It does create curious effects, and that might be useful to some people.
Much more discussion in the accompanying text file: plugin-trace-notes.