www.pudn.com > _LevelSet.rar > Demo2.m

% This Matlab file demomstrates a variational level set method that improves the original method in Li et al's paper 
%    "Level Set Evolution Without Re-initialization: A New Variational Formulation" 
%    in Proceedings of CVPR'05, vol. 1, pp. 430-436. 
% Author: Chunming Li, all rights reserved. 
% E-mail: li_chunming@hotmail.com 
% URL:  http://www.engr.uconn.edu/~cmli/ 
 
clear all; 
close all; 
Img = imread('twoObj.bmp');  % synthetic noisy image 
Img=double(Img(:,:,1)); 
sigma=1.0;    % scale parameter in Gaussian kernel for smoothing 
G=fspecial('gaussian',15,sigma); 
Img_smooth=conv2(Img,G,'same');  % smooth image by Gaussiin convolution 
[Ix,Iy]=gradient(Img_smooth); 
f=Ix.^2+Iy.^2; 
g=1./(1+f);  % edge indicator function. 
 
epsilon=1.5; % the papramater in the definition of smoothed Dirac function 
 
timestep=5;  % time step 
mu=0.04;  % coefficient of the internal (penalizing) energy term P(\phi) 
          % Note: The product timestep*mu must be less than 0.25 for stable evolution 
 
 
lambda=5; % coefficient of the weighted length term Lg(\phi) 
alf=3;   % coefficient of the weighted area term Ag(\phi); 
           % Note: Choose a positive(negative) alf if the initial contour is outside(inside) the object. 
            
% define initial level set function (LSF) as -c0, c0 at points outside and inside of a region R, respectively. 
[nrow, ncol]=size(Img);   
c0=3;    % The constant value used to define binary level set function as initial LSF; 
         % Using larger value of c0 usually slow down the evolution. 
initialLSF=c0*ones(nrow,ncol); 
w=12; 
initialLSF(w+1:end-w, w+1:end-w)=-c0;  
u=initialLSF; 
figure;imagesc(Img, [0, 255]);colormap(gray);hold on; 
[c,h] = contour(u,[0 0],'r');                           
title('Initial contour'); 
 
 
% start level set evolution 
for n=1:300 
    u=EVOLUTION_LSD(u, g ,lambda, mu, alf, epsilon, timestep, 1);      
    if mod(n,20)==0 
        pause(0.001); 
        imagesc(Img, [0, 255]);colormap(gray);hold on; 
        [c,h] = contour(u,[0 0],'r');  
        iterNum=[num2str(n), ' iterations'];         
        title(iterNum); 
        hold off; 
    end 
end 
imagesc(Img, [0, 255]);colormap(gray);hold on; 
[c,h] = contour(u,[0 0],'r');  
totalIterNum=[num2str(n), ' iterations'];   
title(['Final contour, ', totalIterNum]); 
 
figure; 
mesh(u); 
title('Final level set function');