Abstract: To realize the vectorization of 2D engineering CAD drawings, a vectorization method based on the recognition of object legends and their topology is proposed. The method firstly proposed a classification method for multi-class object legends based on HOG and SVM by using the geometric properties of object legends; Then, the annular segmentation feature of objects was extracted to recognize subclass object legends; Finally, Object legends’ Topology was recognized by the method based on connected components labeling. Experimental results demonstrate that the proposed algorithm is able to efficiently recognize the objects and their topology relation in the drawings and is robust to the fractured and fuzzy lines. The extracted geometric and topological information can lay the foundation for subsequent vectorization of drawings. Besides, the exploratory research of related technologies in this thesis is also instructive to the fellow-up study of engineering drawings vectorization.

Key words: 2D engineering CAD drawing, vectorization, classification, recognition, topology connection, HOG, connected components labeling