Opencv 通过形态学操作实现图像边缘。 首先将图像转换为二值图像，然后膨胀此二值图像，最后减去未膨胀之前的图像便得到了图像的边缘。-Opencv realize the image edge by morphological operations. First, convert the image to a binary image, and then expanded this binary image, the last image before subtracting the