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
Presently, man-machine interface development is a widespread research activity. A system to understand hand drawn architectural drawings in a CAD environment is presented in this paper. To understand a document, we have to identify its building elements and their structural properties. An attributed graph structure is chosen as a symbolic representation of the input document and the patterns to recognize in it. An inexact subgraph isomorphism procedure using relaxation labeling techniques is performed. In this paper we focuse in how to speed up the matching. There is a building element, the walls, characterized by a hatching pattern. Using a Straight Line Hough Transform (SLHT) based method, we recognize this pattern, characterized by parallel straight lines, and remove from the input graph the edges belonging to this pattern. The isomorphism is then applied to the remainder of the input graph. When all the building elements have been recognized, the document is redrawn correcting the inaccurate strokes gotten in a hand drawn input.
Keywords: Line drawings, Hough transform, Graph matching, CAD systems, Graphics recognition.