Research And Application Of Sketch Beautification And Understanding In Vector Engineering Drawings Retrieval

With the rapid development of the information technology, the electronic vector engineering drawings are gradually playing important roles in all walks of life replacing the traditional paper files. However, it is still a difficult work to obtain required drawing documents from the database quickly and conveniently. Currently, the drawing documents retrieval is usually accomplished based on the keywords, such as project name, designer and document number. Keyword-based retrieval technology is fast and simple, whereas manual labeling takes a lot of troubles. Moreover, it is not easy to describe the content in vector engineering drawings with words.As a result, the paper proposes a novel sketch-based vector engineering drawings retrieval technique, which belongs to the content-based image retrieval technology. The major research emphasizes on the graphic features of documents rather than keywords, which makes the retrieval more direct and clear. Furthermore, this retrieval technique is more convenient for users to express their retrieval intention when the hand-drawn sketches are used directly as the retrieval conditions.After deep investigation on the sketches recognition and drawings retrieval technique, this paper presents a system framework of the vector engineering drawings retrieval technology based on hand-drawn sketches, and realizes a prototype system as well. The main researches are:(1) Presents sketch-based engineering drawings retrieval framework. The framework is composed of retrieval condition preprocessing, sketch beautification, the uniform representation model construction, shape matching with model descriptor and relevance feedback.(2) Proposes a sketch beautification method based on stroke partition. First, preprocesses stroke. Then, to segmenting the stroke adaptive, we use a method based on error fitting to find the corners. Finally, beautifies the stroke by their underlying primitives (lines, curves and arcs).(3) Proposes a uniform representation model between the sketch and vector engineering drawings. To be aimed the misunderstanding brought by the graphic visual ambiguity in the sketch, a model based on surrounding area of the smallest hole with spatial relations is presented. And this model can be used as the uniform representation model between the vector engineering drawings and sketch. On this basis, two kinds of features are considered, i.e., combining shape and topology with spatial relationship, to filter the database documents and gradually narrow the search scope. Consequently, we improve the efficiency of the retrieval system.(4) Completes the design and development of the sketch-based engineering drawings retrieval system .Besides, the three main components of this system are described in detail.