图像减操作，对图像进行灰度化，腐蚀预处理，之后进行用原图像减去处理后的图像，再对图像进行平滑处理，能有效去除图像背景中的噪声-Subtraction image, the image gray, etching pretreatment, after subtracting the processed image with the original image, and then the image smoothing, can effectively remove noise in the i