lvmskel(3)

LIBRARY ROUTINE
lvmskel - Computes the skeletonization of a binary byte image

LIBRARY CALL
#include "vinclude.h"
int
lvmskel(image)
struct xvimage *image;

INPUT

    image _ xvimage structure

OUTPUT

    image _ holds the result.

MODIFICATIONS
Ghosted by Pascal Adam on june the 1st 1990

DESCRIPTION
vmskel computes the skeleton of a binary byte image using a fixed disk as the structuring element.

SKELETON
The skeleton or medial axis algorithm thins by creating an archetypal stick figure that internally locates the central axis of the figure. The skeleton of a set S, in the Euclidean plane is defined in the following manner:

    For each x in S, let D(x) denote the largest disk centered at x such that, D(x) is a subset of S. Then x is in the skeleton of S if there does not exist a disk, Ds, not necessarily centered at x, such that Ds properly contains D(x) and Ds is contained in S.

There are several ways to define a digital version of Euclidean disks; we will use square disks. This method is used in the book referenced at the end of this description.

This method does not guarantee a continuous skeleton, but does guarantee a thin skeleton.
Also, the skeleton of a square, rectangle, etc. can be substantly different from the classic result obtained in continuous morphology.

ADVICE:

    For this skeleton function, all grey levels different from 0 are considered "white" or equivalent to 255. Therefore, the image is not required to be binary, however, it is strongly advisable to use vthresh on grey level images before using any morphological function.

These algorithms are issued from :

    "Morphological Methods in Image and Signal Processing"
    Charles R.Giardina
    Edward R. Dougherty
    Prentice Hall, Englewood Cliffs, New Jersey 07632

SEE ALSO
vmskel(1), intro(3), vipl(3), verror(3), vutils(3) vmdilate(1), lvmdilate(3), vmerode(1), lvmerode(3), vmopen(1), lvmopen(3), vmclose(1), lvmclose(3), vxor(1), lvxor(3)

RESTRICTIONS
vmskel accepts only BYTE images , and it is strongly advisable to use vthresh to binarize the image before eroding it.

AUTHOR
Pascal ADAM

COPYRIGHT
Copyright 1991, University of New Mexico. All rights reserved.