Automatic Placement Of The Labels On The Vectorgraphs

The paper analyzes the problem of automatically placing the labels on the work-piece described in the form of vector-graphs. The problem is considered as placing a given a rectangle (or a array of rectangles connecting to each other) in the vector multiply connected domain. The placement of the labels has to avoid both the boundarieys and the marks on the graph. Taking one thing with another, the placement problem is decomposed as four sub-issues. The issues are vector graph rasterizer, region filling of the binary image, computing the main direction of the vector graph and some other assistant processions.DXF documents is a kind of vector graph document in form of ASCII, and it is used as the information communication intermediary between CAD system and extern facilities or between one CAD system and another. The strongpoint of the DXF document makes it the latent criterion in industry. A graph can not be processed unless it is convert to a grid image. The vector graphs in this paper is processed by a special method in the idea of raster so that it can be deal with as a image.Region filling algorithms is a fundamental and important research branch in image processing. The multiply domain to place the label is complex and the region filling task in the paper is different from common method in the image processing. So, a new method based on scan-line and Freeman chain-code is provided to deal with the region filling in the multiply connected domain.In a image, the pixels are placed in the horizontal and vertical directions. The labels usually can not be filled in the strip graph when the main direction of the graph is neither horizontal nor vertical. In this paper , PCA method is used to process the discrete points on the boundary and the marks to compute the main direction of the work-piece graph. When the PCA dose not work, we can also compute the main direction from the longest marks.Combine the solutions of the four issues, a software system is build up. The system take DXF document as input and the output the position and the angle of the labels placed on the work-piece. The system run fast and accurately.