Josep Lladós1, Jaime López-Krahe2, Enric Martí1
1Computer Vision Center - Dep. Informàtica.
Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
2Dep. Informatique, Lab. ai/mime.
Univ. Paris 8, Saint Denis, 93526 Paris CEDEX 02, France
This paper presents a system to understand hand drawn architectural drawings in
a CAD environment. The procedure is to identify in a floor plan the building
elements, stored in a library of patterns, and their spatial relationships. The
vectorized input document and the patterns to recognize are represented by
attributed graphs. To recognize the patterns a such, we apply a structural
approach based on subgraph isomorphism techniques. In spite of their value,
graph matching techniques do not recognize adequately those building elements
characterized by hatching patterns, i.e. walls. Here we focus on the
recognition of hatching patterns and we develop a straight line Hough transform
(SLHT) based method in order to detect regions filled in with parallel straight
lines. This allows not only to recognize filling patterns, but it actually
reduces the computational load associated to the subgraph isomorphism
computation. The result is then that the document can be redrawn by editing all
the patterns recognized.