how to connect disjoint pixels on image borders?

i have an image,i used open close by reconstruction,and then sobel edge detector,it detect edge ,but it has some disjoint parts,pixels are not connected in some parts,i want to use connected component labeling and watershed segmentation,so first i should make a connected border,then use imfill,to fill the area between borders,and watershed to segment them,is there any function i call to connect pixels which are close to each other?when i use sobel on original image,it detects border,but by too many dots,which are not connected,like some one draw borders by dots,when i use open close on image,the border is much better,but still has some disjoint parts,thank you so much