Contour line extraction from color images of scanned maps

Abstract

This paper reports our work on contour line extraction from color images of scanned maps. Color processing extracts the basic colors of an image by switching from RGB to L*a*b color space, projecting the image on its principal axes and using modified histogram splitting. After the user has selected one of the extracted colors, pixel color classification yields a binary image that is thinned for connected-component analysis. Line extraction and merging follows, along with contour line formation based on connectability between the line segments.