Line recognition algorithm using Constrained Delaunay Triangulation

Vectorization, i.e. raster-to-vector conversion, is a central part of graphics recognition problems. Graphics recognition is concerned with the analysis of graphics-intensive documents, such as technical drawings, maps or schemas. In this paper we present a generic algorithm for line extraction based on image vectorization. A pre-processing step provides points that are judged to belong to linear forms. We use Constrained Delaunay Triangulation and an edge filtering process to pass from the raster format to a set of polygons that make up the vector image. The final results are provided by skeletonization of the obtained polygons. The algorithm is automatic with very little interaction from the users and has very satisfying results when tested on road segments.