为了更好地描述曲线,引入了一种有效的曲线编码和描述方法———曲线树。这种曲线树是采用树的结构来描述曲线,其内部元素是有向相对高度。由于任何一种曲线都与一个曲线树一一对应,因此从树的根部开始,取其前几层得到的树,都是对该曲线的粗略的描述,而且随着层数的增加,刻画曲线的精度就越高。这种方法最大的一个优点是它不随曲线平移、拉伸和旋转而变化。在这种曲线描述的基础上,可进一步定义两曲线的距离,以便用来衡量曲线间的相似程度。

A novel approach,curve tree,is proposed for curve representation and encoding.Binary trees composed of directed relative height are adopted to describe curves.Any curve corresponds to a curve tree.We may take the first n levels of the curve tree,which compose a binary tree roughly describing the curve.The more levels we get,the finer it describes the curve.The representation is invariant to rotation,scaling,and translation.Based on this descriptor,curve distance is defined to weigh the similarity between curves.