中文说明：本代码实现了Harris的角点特征提取：计算图像亮度f(x,y)在点(x,y)处的梯度、构造自相关矩阵、提取特征点、在计算完各点的值后，进行局部非极大值抑制
English Description：
This code implements the Harris corner feature extraction: image brightness of f (x, y) at point (x, y) gradient, autocorrelation matrix is constructed, at extracting feature points, calculate the value when you are finished, partial non-Maxima suppression