说明：   Sobel算子是一阶导数的边缘检测算子，在算法实现过程中，通过3×3模板作为核与图像中的每个像素点做卷积和运算，然后选取合适的阈值以提取边缘。
(The Sobel operator is the edge detection operator of the first derivative. During the algorithm realization, the 3 × 3 template is used as the convolution sum of each pixel in the kernel and image, then the appropriate threshold is selected to extract the edge.)