matlab 程序解释 急需

Question

求助～！！急 程序解释
下面是用水平集算法的图像分割程序，哪位高手帮忙大概解释一下 特别是图像显示的那一块（红色字体的是在调用evolution.m）急用～～

Img = imread('t11.jpg'); % The same cell image in the paper is used here
Img=double(Img(:,:,1));
sigma=1.5; % 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, try timestep=10, 20, ..., 50, ...
mu=0.2/timestep; % coefficient of the internal (penalizing) energy term P(\phi)
% Note: the product timestep*mu must be less than 0.25 for stability!
lambda=5; % coefficient of the weighted length term Lg(\phi)
alf=1.5; % coefficient of the weighted area term Ag(\phi);
% Note: Choose a positive(negative) alf if the initial contour is outside(inside) the object.

[nrow, ncol]=size(Img);
figure;imagesc(Img, [0, 255]);colormap(gray);hold on;
text(6,6,'Left click to get points, right click to get end point','FontSize',[12],'Color', 'r');
% Click mouse to specify initial contour/region
BW = roipoly; % get a region R inside a polygon, BW is a binary image with 1 and 0 inside or outside the polygon;
c0=4; % the constant value used to define binary level set function;
initialLSF= c0*2*(0.5-BW); % initial level set function: -c0 inside R, c0 outside R;
u=initialLSF;
[c,h] = contour(u,[0 0],'r');
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(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
close ('figure 1')
close ('figure 2')
axes(handles.fgh);
imagesc(Img, [0, 255]);colormap(gray);hold on;
[c,h] = contour(u,[0 0],'r');
totalIterNum=[num2str(n), ' iterations'];
我是超级菜鸟

Answer 1

在这里：
function u = EVOLUTION(u0, g, lambda, mu, alf, epsilon, delt, numIter)
% EVOLUTION(u0, g, lambda, mu, alf, epsilon, delt, numIter) updates the level set function
% according to the level set evolution equation in Chunming Li et al's paper:
% "Level Set Evolution Without Reinitialization: A New Variational Formulation"
% in Proceedings CVPR'2005,
% Usage:
% u0: level set function to be updated
% g: edge indicator function
% lambda: coefficient of the weighted length term L(\phi)
% mu: coefficient of the internal (penalizing) energy term P(\phi)
% alf: coefficient of the weighted area term A(\phi), choose smaller alf
% epsilon: the papramater in the definition of smooth Dirac function, default value 1.5
% delt: time step of iteration, see the paper for the selection of time step and mu
% numIter: number of iterations.
%

u=u0;
[vx,vy]=gradient(g);

for k=1:numIter
u=NeumannBoundCond(u);
[ux,uy]=gradient(u);
normDu=sqrt(ux.^2 + uy.^2 + 1e-10);
Nx=ux./normDu;
Ny=uy./normDu;
diracU=Dirac(u,epsilon);
K=curvature_central(Nx,Ny);
weightedLengthTerm=lambda*diracU.*(vx.*Nx + vy.*Ny + g.*K);
penalizingTerm=mu*(4*del2(u)-K);
weightedAreaTerm=alf.*diracU.*g;
u=u+delt*(weightedLengthTerm + weightedAreaTerm + penalizingTerm); % update the level set function
end

% the following functions are called by the main function EVOLUTION
function f = Dirac(x, sigma) %水平集狄拉克计算
f=(1/2/sigma)*(1+cos(pi*x/sigma));
b = (x<=sigma) & (x>=-sigma);
f = f.*b;

function K = curvature_central(nx,ny); %曲率中心
[nxx,junk]=gradient(nx);
[junk,nyy]=gradient(ny);
K=nxx+nyy;

function g = NeumannBoundCond(f)
% Make a function satisfy Neumann boundary condition
[nrow,ncol] = size(f);
g = f;
g([1 nrow],[1 ncol]) = g([3 nrow-2],[3 ncol-2]);
g([1 nrow],2:end-1) = g([3 nrow-2],2:end-1);
g(2:end-1,[1 ncol]) = g(2:end-1,[3 ncol-2]);

Answer 2

d

Answer 3

楼主现在会了没？我也急用啊