说明：  如果图像中的目标物体是连接在一起的，则分割起来会更困难，分水岭分割算法 经常用于处理这类问题，通常会取得比较好的效果。分水岭分割算法把图像看成 一幅“地形图”，其中亮度比较强的区域像素值较大，而比较暗的区域像素值较 小，通过寻找“汇水盆地”和“分水岭界限”，对图像进行分割。
(Separating touching objects in an image is one of the more difficult image processing operations. The watershed transform is often applied to this problem. The watershed transform finds "catchment basins" and "watershed ridge lines" in an image by treating it as a surface where light pixels are high and dark pixels are low. )