A Knowledge-Aided Line Network Oriented Vectorisation Method for Engineering Drawings

A Novel Knowledge-Based System for Interpreting Complex Engineering Drawings: Theory, Representation, and Implementation

“…Existing engineering interpretation methods may be roughly classified into five categories, depending on the basic technique they rely on: pixel-level knowledge-independent [6], [7], [9], [10], [11], [22], [23], pixel-level knowledge-dependent [13], [16], [17], [18], [20], [24], [25], [26], [27], [28], [29], vectorial-level knowledge-independent [30], [31], [32], [33], vectorial-level knowledge-dependent [34], [35], [36], [37], [38], [39], and hybrid systems [8], [40], [41].…”

“…Dori and Liu [45] design an improved MDUS system, whose core is a hierarchy of graphic object classes, each containing specialized object recognition algorithms. Other knowledge-aided systems have been proposed to search line networks [18], dimensions [26], or geometric structure [17] from paper drawings. However, the knowledge in these systems is still in low-level forms and only simple entities can be extracted.…”

“…Earlier, our research group designed a series of low-level algorithms for engineering drawing analysis [18], [22], [23], [24], [25]. We later continued our research to high-level recognition and 3D reconstruction [26], [38], [39], [47], [48].…”

“…First, how to represent contextual knowledge that describes drawing conventions efficiently and robustly is admittedly a hard problem [3], [4], [41]. Some knowledge-based systems use the "rules + inference" representations to obtain low-level vectors [8], [16], [17], [18], [19], [20], [21]; however, such unstructured rules are not amenable to content-oriented analysis due to their limited ability to describe complex relations of various types of high-level entities in real-life engineering drawings. Second, a real-life drawing does not only contain geometric shapes but also indicates their constraints and interactions.…”

A new approach for line recognition in large-size images using Hough transform

“…Instead, we use an intersection-preserving approach based on detecting the trends of branches at the intersection [9]. It simply removes those parts whose local line widths are less than or similar to the line width of this line segment as rectangular areas.…”