A Vectorization Algorithm of Closed Regions in Raster Images

In this paper we present an algorithm, which vectorize geographical images. The transformation from a raster representation to a vectorial one is a question that has to be frequently treated in the management and processing images. For example the geographical information is readily available on photos, maps, planimetries. These documents contain characters, symbols and graphical parts. Usually the text and symbols detection phase in pattern recognition algorithms and in vectorization algorithms for geographical images is followed by the recognition of geographical closed regions and image vectorization. We give a description of the proposed algorithm starting from the assumption that the input image is given by an array of pixel. Boundaries of closed regions are represented by black pixels located above a white background. The algorithm uses a representation based on coding horizontal sequences of black pixels identified in the image. The algorithms consists of two steps: the first one identifies horizontal sequences of black pixels and stores them in a list L, the second step read the list L for storing boundaries of the identified regions in a new list R.