With the different view of traditional methods

in the light of the topological theory

this paper studies a new method for converting raster data to vector data. Compared with traditional methods

the new method does not need to pro process the raster image

created topological structure of vector data during the conversion. This method processed raster data row by row just one time

and could fit for large image. It

therefore

has high efficiency high speed

and gives good experimental results.