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#### lsnakes

Name

lsnakes Level Set implementation of the Snakes Model

Command Synopsis

lsnakes [-n Niter] [-t thre] [-f force] in ref out

-n Niter : number of iterations, default 1

-t thre : threshold to binarize mask images, default 1.0

-f force : force term, default 0.0001

in : input contour (Fimage mask)

ref : input reference Fimage

out : output contour (Fimage mask)

Function Summary

Fimage lsnakes (in , ref , Niter , thre , force )

Fimage in ;

Fimage ref ;

int *Niter ;

float *force , *thre ;

Description

This module implements the classical snakes model using a level set formulation [CCCD93]. It moves a snake image (image of contours) according to the content of a natural image ref, in order to fit the contours of the object enclosed in each initial contour.

The initial snake Fimage is in (u = u0): the inside of each snake is represented by values smaller than the threshold thre (-t option). Such an image can be generated from a polys structure using the module fillpoly.The polys structure may itself be interactively created using the readpoly module.

The module lsnakes evolves u0 with an evolution PDE, and generates a new snake image out. This output can be used as a new input of lsnakes, together with ref, to continue the motion. When the last snake image is obtained, a final image containing the natural image with the contours found can be generated using the modules emptypoly and fmask.

Geometric Active Contours Equation :

with    g(x) = .

• = positive real constant which represents a force.
• g0 = image where we are looking for the contour of the object.
• G(x) = C12exp(- ) a Gaussian.

Version 1.0

Last Modification date : Fri Apr 11 09:33:27 2003

Author

Francoise Dibos, Jacques Froment, Kamal Lakhiari

Next: lsnakes_demo Up: Reference Previous: emptypoly   Contents   Index
mw 2004-05-05