* Read image in 
read prak1 
* set color display in color mode 
don,3 
* set timer on 
ton 
* clear all bitplanes of image B 
clear,B 
* threshold image, using automatic threshold 
thr 
* invert image to obtain white objects in black background 
inv 
* make a copy of the image 
bcop 1,3 
* calculate skeleton 
skel 
* Find branchpoints 
vertices 
* propagate what remains (the closed contours) into the original image 
propag 500,1,3,8,0,B