1. A method for identifying a border between a skin lesion and surrounding skin on a digital image of a skin lesion comprising: a. preprocessing the image to identify pixels that represent features other than skin and lesion; b. determining a first lesion ratio estimate of the image using bounding box methods; c. determining a first lesion ratio estimate of the image using a mean lesion ratio estimate if one or more bounding box sides is not found and using the mean lesion ratio estimate to approximate the location(s) of any missing bounding box sides, if possible; d. subsequently applying a lesion ratio offset to produce a corrected lesion ratio estimate by running a classifier algorithm that incorporates color and histogram data from both inside an inner bounding box and outside an outer bounding box if such bounding boxes were found previously; and e. inputting said corrected lesion ratio estimate into a watershed algorithm for identifying a border between a skin lesion and surrounding skin.