在工程图纸矢量化中引入了平均链码和线条的概述，阐述了平均链码与直线链码的关系，提出了确定线条边界的切向和法向，线条检测，线条两侧同步跟踪以民折处理的方法。以此实现直线或微弯曲线的整条提取，跟踪的同时实现图文的磁量化速度和质量有较大的提高。

This paper gives new definitions of line and average chain code, out lines the relation of average chain code and straight line chain code, and proposes the mechanism of line detecting and line contour tracking method. Based on this method, we successfully extract straight lines and smoothly bend lines and separate text from image while tracking. This method can greatly improve the quality of vectorization and have a higher processing speed. It also can be used to detect and extract lines in other fields.