说明：  sobel算法的源码,应用2个3x3的掩模中心像素（mask）检测图像的边缘。一个是检测水平边沿的 ；另一个是检测垂直平边沿的。可以自己测试和修改参数，从而得到最佳的算法值。
(sobel algorithm source code, the application of two 3x3 pixel mask center (mask) image edge detection. One is the detection level of the edge the other is the detection of vertical edges of the ping. Able to test and modify the parameters of the algorithm in order to get the best value.)