Visual Structure Analysis of Flow Charts in Patent Images

This report presents the work carried out for the flow chart recognition task in the course of the CLEF-IP 2012 competition. The goal is to obtain structural information of flow charts based on the visual content of the images. To this end, for each flow chart a list of its nodes and their interconnections, i.e. its edges, is extracted and the type of the nodes and edges and attached text is recognized. The automatic recognition task is done in three stages: (1) flow chart image pre-processing using connected component analysis, morphological filters and line segmentation, (2) identification of nodes, junction points, end points and edges and (3) recognition of text, geometric node types and edge directions. Examples demonstrate good recognition results obtained for 100 tested flow chart images.