Abstract: According to the shortage of common curve matching algorithms which can’t process rotation and scaling, a curve matching method of Freeman Chain Code（FCC） is proposed. An inflection point detection algorithm based on the accumulative of FCC and chain code difference is designed. Calculating the start point and the direction of the curves, the inflection point sequence which doesn’t change with rotation and scaling is obtained. The curves are matched by the length and the angle of the inflection point sequence. This method isn’t suffered with rotation and scaling, it has small computation and is easy to realize. The simulation experimental results show that the algorithm is effective and reasonable.

Key words: Freeman chain code, accumulative of difference, chain code difference, curve matching

摘要： 针对普通曲线匹配算法不能处理旋转和缩放曲线的不足，提出Freeman链码描述的曲线匹配方法。该方法为Freeman链码设计一种基于差别累加值及链码差的拐角点快速检测算法，能够快速地检测出曲线拐角点；通过计算曲线起点和曲线方向，得到不随曲线旋转、平移和尺度变化的标准拐角点序列；根据拐角点的长度序列和夹角序列进行相似判断实现曲线匹配。Freeman链码描述的曲线匹配方法不受曲线旋转和缩放的影响，计算量小，易于实现，仿真实验证明该算法合理有效。

关键词: Freeman链码, 差别累加值, 链码差, 曲线匹配