After Vectorization: Converting areas to lines

[Mangkud]

I scanned a map and converted it into a vector graphic using Ilustrator's (CS2) Live Trace.

The results are all closed paths (areas, shapes), but I would like to have lines. How can I convert (or simplify) areas to lines? If I could do that, it would be possible to preserve the topology of the map and I could easily change the general look of all rivers and streets...

Selecting a line path and then "Object > Path > Outline Stroke" kinda does the opposite of what I intend to do.

Excuse me for maybe not using the correct terminology, I am an Illustrator newbie.

Regards,
Markus

 

[Mangkud]

I found another solution: I'm using AlgoLab's raster to vector conversion software now. The have a function that let's you build center lines of objects, not outlines.

 

[nefaste]

Sounds interesting. There's no such feature in Illustrator. Do you have any link on some results of this "center line" function ?

I remember studying algorithms for finding the skeleton of objects, but they were for discete (pixel-based) images.

 

[Mangkud]

I now found out that the Live Trace function IS capable of creating center lines of objects. But the Tracing options have to be really really finetuned to produce useful results. Center lines cannot be created for colored images and you have to be sure that for the 'Trace Settings' the 'Strokes' checkbox is checked. Mainly finetuning the 'Max Stroke Weight' property will produce better results.

A problem is, that Live Trace only creates center lines for small objects. Example: The main streets (pretty wide) of my scanned map are still not recognized as lines and are vectorized as filled areas, whereas the smaller side streets are already identified as line objects.

After downsizing the resolution of my input picture also some parts of the main roads were vectorized as lines, but the result is not satisfying me. It seems arbitrary where Live Trace draws the line

That Raster to Vector Conversion Toolkit from

http://www.algolab.com

is more useful to me right now, so I'll stick with that.