Thanks Stefan, that indeed sounds like most reasonable first step I should take, instead tangling myself in Voronoi diagrams from start. Thinking about it and possible reasons why I didn't see such approach mentioned, I thought about another possible extension, and I'll explore both tomorrow - after segmenting lines by color, and thinning I could apply smooth vector tracer on lines as they are (with gaps) so that I'll get spline fit in vector format; then instead programming search for tools supporting any vector format that can get me to it. Perhaps some GIS tool, or maybe just some utility tool useful elsewhere, and then decide next step.<br>