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lsnakes

$ \bigcirc$Name


lsnakes Level Set implementation of the Snakes Model




$ \bigcirc$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)




$ \bigcirc$Function Summary


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

Fimage in ;

Fimage ref ;

int *Niter ;

float *force , *thre ;




$ \bigcirc$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 :

$\displaystyle \left\{\vphantom{
\begin{array}{ll}
\displaystyle
\frac {\parti...
...imes R^2} \\
\\
u(0,x) = u_0(x) \qquad
x\in{R^2}
\end{array}
}\right.$$\displaystyle \begin{array}{ll}
\displaystyle
\frac {\partial u}{\partial t} =...
...,\infty[ \times R^2} \\
\\
u(0,x) = u_0(x) \qquad
x\in{R^2}
\end{array}$

with    g(x) = $\displaystyle {\frac{{1}}{{1+\vert\nabla G_\sigma \ast u_0\vert^2}}}$.




$ \bigcirc$See Also


lsnakes_demo.


$ \bigcirc$Version 1.0


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


$ \bigcirc$Author


Francoise Dibos, Jacques Froment, Kamal Lakhiari






next up previous contents index
Next: lsnakes_demo Up: Reference Previous: emptypoly   Contents   Index
mw 2004-05-05