为MATLAB中的图形增加标签，从而可以有效地表示图形意义，防止读不懂图的情况-　　BWLABEL supports 2-D inputs only, whereas BWLABELN support any

　　input dimension.　In some cases you might prefer to use BWLABELN even

　　for 2-D problems because it can be faster.　If you have a 2-D input

　　whose objects are relatively "thick" in the vertical direction,

　　BWLABEL will probably be faster　otherwise BWLABELN will probably be

　　faster.