Recognition of thick closed polygons in engineering drawing images

The paper considers the problem of automatic input and vectorization of engineering drawings. One of the most difficult tasks in this problem is recognition of ED entities. We propose the algorithm to recognize one of the ED entities namely blocks or closed 'thick' polygons in engineering drawings. The algorithm is based on ED image vectorization and takes into account parameters of vectorized segments, tests several alternative extensions for a path, and chooses the best one among several alternatives. It has been verified experimentally on real ED images and has shown good results. In conclusion of the paper, some technical parameters of experiments are given.