how to get contour from an image?

hi im trying to reimplementation a paper for research.. the paper title is HAZARDOUS MATERIAL SIGN DETECTION AND RECOGNITION by Albert Parra, Bin Zhao, Andrew Haddad, Mireille Boutin, Edward J. Delp

in this paper image is processed by some kind of sequential series of image processing method just like : get saliency map -> treshold map -> salient region found-> detect using specific color channels and grayscale by tresholding them -> dilation to merge area -> GET CONTOURS

in matlab studio can i get contour from dilation output? please give me an example how to do it

thanks matlab