Study On Raster Vector Conversion

Nowadays, the technology of automatic input and recognition of engineering drawing has become a hot spot in the field of CAD/CAM. A general way to do the work is to scan drawing into computer, then automatically convert raster images to vector ones through algorithm of vectorization. High efficiency can be achieved in this way, but precision remains to be improved.After a long-term study and practice, it is found that the approach combining both automatic and manual method, which pays equal attention to both efficiency and quality, can get a better effect in practice. Furthermore, this approach can save time and speed up the processing because of the scientific procedures it uses, in which at first the drawing is automatically vectorized and then modified manually. Accordingly, this approach has become more and more popular. In the past years, many vectorization algorithms have been proposed, some of which focus on parts, some of focus on the whole, both of them have produced some effects, but they are far from practical stage. This is due to the diversity and complexity appeared in its applications.On the basis of widely consulting the material about engineering drawings in the aspects of input and recognition at home and abroad, this paper presents an efficient vectorization algorithm-a vectorization algorithm for engineering drawing based on thinning and adaptive windows technology. This approach works with vectorization both in the partial and overall aspects and it not only gives full reins to the strong points of the thinning method but also successfully avoids the distortion by using the technology of adaptive windows to extract the vectors at cross point. Besides, as for the vectorization of the raster images with arbitrary shapes and filled fields, which is more complicated than engineering drawing, this paper also makes some tentative discussion and works out some controllable vectorization algorithm accordingly. The image pre_processing which is involved in the process of the vectorization of raster images, has also been detailedly discussed in this paper. The technology of image pre_processing includes the process of drawing_scanning, image_binarization, image_translation and soundoff.It is elaborated in the experiment that a better graph effect can be obtained by using the technology of vectorization of raster images, which is proposed by this paper.