Getting the curve border from a black white image is very important in CAS/CAD/CAM. A new algorithm for it is presented. The main idea of this algorithm is auto segment of edge points and quick Bezier fitting to those points. In this algorithm

edge points of a black white image are detected firstly. At second step

these edge points are segmented according to left and right direction of every point. Then

these segments are classified into two kinds: curve segment and line segment. Those points on the curve segments will be fitted into Bezier curves using a certain simple and quick method. In this way

a set of border from a black white image

which consists of lines and Bezier curves

is presented. Comparing to the vector method

this algorithm can get accurate and smooth border of a black white image which is not distorted even if it is enlarged many times

so it is easy to output the border of a black white image to devices such as sign maker

plotter

CNC machine

etc. This algorithm is efficient

and widely used in serial software "Wentai Kehui"

the speed and result of which are as good as the same kind of software made in developed countries.