In this communication some algorithms for polygonal approximation of closed digital curve under a non-parametric framework are compared with an unsupervised approach to polygonal approximation. The two approaches are compared with respect to number of vertices, maximum error, measures $W{E}_{\infty }$ and $W{E}_2$, Rosin’s measure and relative execution time. The algorithms are tested using images from MPEG7 dataset and it is observed that the algorithms under non-parametric framework produce too many vertices many of which are redundant resulting in rough approximations whereas the unsupervised approach produces less number of vertices with low value of $W{E}_{\infty }$ and $W{E}_2$ leading to smooth approximations and high value of Rosin’s measure, but its relative execution time is high.

在此通信中，将非参数框架下闭合数字曲线的多边形逼近的一些算法与多边形逼近的无监督方法进行了比较。比较两种方法的顶点数，最大误差，量度$\mathrm{w\; ^}{Ë}_{\infty }$ 和 $\mathrm{w\; ^}{Ë}_2$，松香的量度和相对执行时间。使用来自MPEG7数据集的图像对算法进行了测试，结果发现，非参数框架下的算法会产生过多的顶点，其中许多是多余的，从而导致粗略的近似，而无监督的方法会产生较少的顶点，且具有较低的$\mathrm{w\; ^}{Ë}_{\infty }$ 和 $\mathrm{w\; ^}{Ë}_2$ 导致平滑近似和松香测度的高价值，但其相对执行时间较长。