How to Win a Dashed Line Detection Contest

Dov Dori, Liu Wenyin and Mor Peleg


Correct recognition of dashed lines is essential for high-level technical drawing understanding. Automatic solution is quite difficult due to the limitations of machine vision algorithm. In order to promote development of better techniques, a dashed line detection contest was held at the Pennsylvania State University during the First International Workshop on Graphics Recognition, August 9-11, 1995. The contest required automatic detection of dashed lines on tesst drawings at three difficulty levels: simple, medium and complex, which contained dahsed and dash-dotted lines in straight and curved shapes, and even interwoven texts. This paper presents dashed line detection techniques which won the first place in the contest. It successfully detected the dashed lines in all drawings. The underlying mechanism is a sequential stepwise recovery of components that meet certain continuity conditions. Results of experiments are presented and discussed.