工程图纸扫描输入与识别理解是CAD推广和普及的关键步骤之一,主要解决已有大量图纸再利用问题.在工程图纸扫描图象识别研究中,圆弧识别是识别算法中的重点和难点.传统的圆弧识别多是基于线段逼近.该文提出一种基于单义域邻接图的圆弧及圆识别算法,可以直接提取圆弧.对二值图象作水平黑游程编码,相关游程基于线宽与拓扑的一致性构成条形域,对其中多义域进行分裂得单义域(线段域和圆弧域).单义域邻接图可较好描述图象的几何属性与拓扑关系.单义域具有明显的形状意义(线段、圆弧、箭头等),提高了识别的整体性.圆弧及圆的识

The scanning input and recognition of engineering drawings is a key step in CAD, and is to reuse lots of engineering drawings. In study on recognition of scanned image of engineering drawings, the recognition for circular arcs is an important and difficult problem. Recent algorithms of recognizing arcs are mainly about approximation with lines. This paper presents an algorithm for recognizing arcs and circles using Primitive Regions Adjacent Graph, which can directly extract arcs. The binary image is encoded with black horizontal runlength. A stripe region consists of correlative runlengths with the same width and topology. The stripe regions then can be segmented as some primitive regions (line and arc). The graph is used to describe geometrical property and topological constraint. The primitive region supplies shape information (line, arc, arrow etc.) improving integrality of recognition. After extraction of the arc region from regions, the seed for an arc is obtained. By traversals for the graph, the seed arc grows by constrains for the same circle. Some applications to recognize arcs and circles are finally provided, which show that the algorithm is effective and robust, can solve well intersection and tangency of between an arc and a line or an arc.