中文说明： 本代码实现用离散二维卷积处理图像。卷积（Convolution）是一个常用的图像处理技术，可以改变像素强度，从而影响周围其他像素的强度。使用卷积就是为了提取显著特征，减少特征维数，减少计算量。
English Description：
&This code uses discrete two-dimensional convolution to process images. Convolution is a common image processing technology, which can change the intensity of pixels, thus affecting the intensity of other pixels around. Convolution is used to extract salient features, reduce the dimension of features and reduce the amount of computation.