针对工程图样中线段的识别和提取问题，提出了一种提取扫描图象曲线轮廊关键点的算法和相应的提取条件准则，该算法可自动逐行检测扫描行中的黑游程，当相继行中的黑游程满足一定的条件准则时，即可提取出相应的黑游程边界点，并形成关键点，依据这些关键点，利用B样条曲线理论来拟合曲线，最终即可实现对图象曲线的提取，该算法不仅速度快，抗噪声性能强，且提取识别也到得了满意的效果。

The conversion of drawing image into vector form is of important in many fields, especially in the field of electronic and mechanical applications. In this paper, a new approach for extracting determinant contour points of lines in scanned engineering drawings is proposed. This method can not only obtain determinant contour points placed in line contour of the drawing image but also process these points automatically. The basic idea of proposed algorithm is totally different from that of traditional algorithms, it can remedy some deficiencies which are suffered from traditional algorithms and executes successfully without thinning. This algorithm detects black runs on scanning or consecutive scanning lines automatically, and then extracts determinant contour points from scanned engineering drawings, the main idea of the detecting algorithm is that:first,black runs on current scanning line are detected automatically, and determinant contour points are extracted by detecting the edge points of both current black run and the next black run which is on consecutive scanning line if the relevant condition holds. Second,based on the determinant contour points,the extraction of lines from the original drawing image will be done easily by using B spline theory. Experimantal results indicate that the algorithm has higher speed and other advantages.