图像边缘是图像的重要特征，是图像中特性（如像素灰度、纹理等）分布的不连续处，图像周围特性有阶跃变化或屋脊状变化的那些像素集合。该段代码就是对边缘检测的描述。

-The image edge is an important feature of the image, and is the image characteristics (such as pixel gray, texture) distribution of discontinuous place, image characteristics have order around step change or roof of those pixels set of changes. When the code is the descr iption of edge detection.