中文说明：非局部均值去噪代码，《matlab滤波与去噪分析》，值得学习，作为基础的代码学习，不懂的可以查阅书中的公式，以便理解
English Description：
Nonlocal mean denoising code, "matlab filtering and denoising analysis", is worth learning, as the basis of code learning, do not understand can refer to the book formula, in order to understand