基于Canny算子检测图像的边缘 读入一张图片，显示该图片经过canny算子处理后的边缘检测结果（要求不能直接调用canny算子）-Canny operator based on image edge detection of a read into the picture, showing the picture after a canny operator after the deal with the edge detection results (request can not directly call the canny operator)