说明：  该代码实现了以2为因子的图像升采样和降采样功能。 降采样包括使用平滑滤波器(with using the averaging filter)和不使用平滑滤波器(without using the averaging filter)两种方法。 升采样包括像素点直接复制(pixel replication method)和线性插值(bilinear interpolatoin method)两种方法。 降采样方法和升采样方法共有4种组合。程序运行后，给出了一个原始图片和四个结果图片。
(Drop sampling include the use of smoothing filter (with using the averaging filter) and don t use smooth filter (without using the averaging filter) two kinds of methods. Rose sampling including pixels directly copy (pixel replication method) and linear interpolation (bilinear interpolatoin method) two kinds of methods. Drop sampling method and the rise of sampling methods there are four kinds of combination. The program after, are given a primitive pictures and four results pictures.)