A system for automatic vectorization and interpretation of map-drawings

Uchida

2007

Int. J. Image Grap.

Recognition of engineering drawing entities is one of the most difficult stages in engineering drawing interpretation and many attempts to recognize various types of ED entities have been made. In this paper, we review algorithms for the recognition of ED entities, especially dimensions and crosshatching areas. For the recognition of dimensions, we analyze how dimension texts can be separated from graphics and how arrowheads of dimension lines are recognized. We also analyze the recent systems of ED interpretation. Finally, future tasks are discussed. Int. J. Image Grap. 2007.07:709-733. Downloaded from www.worldscientific.com by UNIVERSITY OF CALGARY on 02/05/15. For personal use only. Recognition of Engineering Drawing Entities 711arrowheads are recognized. We review complete or near-complete ED interpretation systems. During the past 20 years, many ED interpretation systems have been developed for automatic or semi-automatic conversion of paper-based EDs to 3D CAD model. Some review material can be found in Refs. 55, 66, 70 and 75. We shall not touch in this paper a character (and other specific symbol) recognition task. There are many papers published for recognition of characters and symbols and we can refer to only several review papers published recently. 12,20,25,49 For editing and 3D reconstruction approaches, which are also omitted here, we can refer to Refs. 9, 10, 13 and 32. ED Entities What are the ED entities?Vectorized ED can be represented in two ways: by graphic primitives or by ED entities. The first representation is rather simple and not always useful. Straight lines, arcs, curves are the most commonly used graphic primitives. They can be grouped for forming more complex primitives, such as chained lines, text blocks, and arrows. Those complex primitives may be further combined into higher-level elements, that is, ED entities such as • contour lines (often represented by solid lines), • symmetry axes (dash-dotted lines), • hidden contour lines (dashed lines), • matter areas (represented by crosshatching), • dimensions (thin lines with arrows, witness lines and so on),• annotation text, and • circles including concentric circles.Examples of some ED entities are shown in Fig. 2.ED entities can be roughly separated into simple and complex ones. Simple ED entities are used for the description for simple ED structures, e.g. a symmetry axis, a crosshatching line, the border of matter area, etc. and can be represented as rather simple combinations of graphic primitives (or their pieces). In Fig. 2. Examples of ED entities; (a) dimension, (b) symmetry axis, (c) crosshatching area, (d) border of crosshatching area, and (e) a set of concentric circles. Among them, (a), (c), and (e) are complex entities and (b) and (d) are simple entities. Int. J. Image Grap. 2007.07:709-733. Downloaded from www.worldscientific.com by UNIVERSITY OF CALGARY on 02/05/15. For personal use only.

Section: Review Of Ed Interpretation Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recognition of Engineering Drawing Entities: Review of Approaches

Uchida

2007

Int. J. Image Grap.

“…In the stripe medial line, black pixels are analyzed using a Crossing number. 1,14 Depending on the Crossing number value, the following situations are extracted: object beginning, end of object, continuation, merging, splitting, node, and an isolated point. In the vectorization output, the segments of objects bounded by end points and nodes are extracted.…”

Section: Image Vectorizationmentioning

confidence: 99%

A Complete System for Interpretation of Color Maps

Bereishik

Homenko

et al. 2002

Int. J. Image Grap.

Self Cite

The paper describes a system and technology for the automatic/interactive interpretation of color maps. Due to the fact that a completely automatic solution is impossible, a combination of automatic and interactive techniques is used. Firstly, color recognition and separation is performed. For automatic map vectorization, a special fast scheme is used. To make digitization more automatic and user-friendly, an interactive digitizing mode has been developed to extract line-based cartographic objects from vectorised data. The system has a powerful and friendly user interface that is described in the paper. The system is used successfully in the digitization of topographic and other types of map.

“…Usually, the technology of ED entities recognition includes two basic processes: image vectorization and ED entities recognition based on the vectorized image. Description of algorithms used for binary image vectorization is given in our paper [6] that have been firstly developed and successfully used for vectorization of map images. However, every image type has its own specifics and let us show how they could be applied to vectorize ED images.…”

Section: Ed Image Vectorizationmentioning

confidence: 99%

“…In this paper, we propose a fast algorithm for recognition of crosshatched areas in engineering drawings that has been developed in frame of our system for ED interpretation [5,6]. At first, we show specifics of ED image vectorization (in difference from direct vectorization technology) that allows to take into account all specifics of ED images.…”

Section: Introductionmentioning

confidence: 99%

Knowledge-based recognition of crosshatched areas in engineering drawings

Advances in Pattern Recognition

Bereishik

Frantskevich

et al. 1998

Self Cite

One of the main tasks in the problem of engineering drawing (ED) automatic input and interpretation is recognition of ED primitives to obtain 2D image representation for further use in CAD systems. This paper presents two-stage knowledge-based algorithm to recognize crosshatched areas in ED images. At the first stage, pure segment chains i.e. simple structure crosshatched area parts satisfying a template description are detected. At the second stage, the final assembly of the area takes place by using the chains assembled at the first stage.