该函数用来计算任意函数的一阶偏导数(数值方法),基于负熵最大的独立分量分析，利用matlab针对图像进行马氏距离计算 。- This function is used to calculate the arbitrary function of the first order partial derivative (numerical methods), Based on negative entropy largest independent component analysis, Using matlab to calculate the Mahalanobis distance for the image.