1. A computerized method, executed on a computer having a storage facility, for automatically determining a centerline of an object in an image, comprising: obtaining an image of the object; dividing the image to a plurality of test areas; defining a limited number of scanning directions; defining a limited number of detection directions; for each of the plurality of test areas assigning one of the scanning directions and one of the detection directions; examining each test area by scanning the image within the test area in the assigned scanning direction and at each scanning step performing a detection operation in the assigned detection direction to thereby designate one pixel within the detection direction as the localized centerline pixel, and thereby obtain a collection of localized centerline pixels corresponding to the centerline within the test area; storing the coordinates of the localized centerline pixels in the storage facility; and, summing up all the localized centerline pixels of all the test areas to thereby calculate the length of the centerline.