腐蚀的作用是消除物体边界点，使目标缩小，可以消除小于结构元素的噪声点；膨胀的作用是将与物体接触的所有背景点合并到物体中，使目标增大，可添补目标中的空洞。(The function of corrosion is to eliminate the boundary point of the object and reduce the target, which can eliminate the noise point smaller than the structural element, and the effect of expansion is to merge all the background points in contact with the object into the object, so that the target can be enlarged and the void in the target can be replaced.)