此类方法的特点是比较简单、计算量小，算法上容易实现，但很少考虑图像中像素的空间位置关系，因此当背景复杂时，容易丧失部分边界信息，造成分割的不完整；针对灰度图像来展开的(The characteristics of this method is relatively simple, small amount of calculation and easy to implement algorithm, but rarely consider the spatial relationship of pixels in the image, so when the background is complex, it is easy to lose a part of the boundary information, resulting in incomplete segmentation for gray image to start;)