How to find center-lind.

Hello. I am trying to extract contour from paper map. and rough extraction is like below image.

next step is skeletonization. And I want to do that by searching center-line of result of rough extraction.

to say detail, I want to find center-line per certain width.

If width of line is less then 5 pixel, search 1 center-line. If Width of line is more then 5pixel, search 2 line(one located in 1/3 and another in 2/3 point from upper boundary).

My english is very bad. So please refer the image.

please help me. I need your help.

[Arun Mathamkode]

How did you perform the rough extraction of the contours? I assume you might have used the color information to do it. Rather than going to the BW morphological operation, did you tried edge detection on the map? If you know what color the contour lines have you can use that information also to detect these lines.