tag:blogger.com,1999:blog-2703091221672544113.post8943825646029467795..comments2023-06-17T05:53:19.605-07:00Comments on A Scratchpad: Chan Vese Segmentation AlgorithmBurak Bayramlihttp://www.blogger.com/profile/02849512629200782790noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-2703091221672544113.post-62239225927024537092012-04-02T12:10:25.221-07:002012-04-02T12:10:25.221-07:00% Compute c1 and c2 as used in the Chan-Vese segme...% Compute c1 and c2 as used in the Chan-Vese segmentation algorithm.<br />% c1 and c2 are given by <br />% c1 = integral(u0*H(phi))dxdy/integral(H(phi))dxdy<br />% c2 = integral(u0*(1-H(phi))dxdy/integral(1-H(phi))dxdy<br />%<br />% If epsilon == 0, we define H as the usual Heaviside function. Then c1 is <br />% the average of the image pixels over the set where phi is >= 0, and c2 is<br />% the average over {phi < 0}. <br />% If epsilon > 0, we use a smoothed version of the Heaviside function with<br />% parameter epsilon.<br /><br />function [c1, c2] = GetAvgs(I,phi,epsilon)<br /><br /> % Non-smoothed calculation<br /> if (0 == epsilon)<br /> n1 = length(find(phi>=0));<br /> n2 = length(find(phi<0));<br /> Iplus = I.*(phi>=0);<br /> Iminus = I.*(phi<0);<br /> c1 = sum(sum(Iplus))/n1;<br /> c2 = sum(sum(Iminus))/n2;<br /> <br /> % Smoothed calculation<br /> else<br /> H_phi = .5*(1+(2/pi)*atan2(phi,epsilon));<br /> c1 = sum(sum(I.*H_phi))/sum(sum(H_phi));<br /> c2 = sum(sum(I.*(1-H_phi)))./sum(sum(1-H_phi));<br /> end<br />endRobert Chttps://www.blogger.com/profile/17374673003716018214noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-62865461691018001792012-04-02T12:09:49.483-07:002012-04-02T12:09:49.483-07:00function y_next = RKstep(tin, yin, dt, rhs, A, b, ...function y_next = RKstep(tin, yin, dt, rhs, A, b, c)<br /> <br /> [s, m] = size(b);<br /> n = length(yin);<br /> K = zeros(n,s);<br /> <br /> for i = 1:s<br /> K(:,i) = rhs(tin + c(i)*dt, yin + dt*(K*A(i,:)'));<br /> end<br /> <br /> % Each column of y_next is the solution calculated using the<br /> % corresponding column of b<br /> y_next = yin*ones(1,m) + dt*(K*b);<br />endRobert Chttps://www.blogger.com/profile/17374673003716018214noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-28668435079671858642012-04-02T12:09:23.700-07:002012-04-02T12:09:23.700-07:00function phit = PhiT(phi,I,epsilon)
[c1,c2] =...function phit = PhiT(phi,I,epsilon)<br /><br /> [c1,c2] = GetAvgs(I,phi,epsilon);<br /> <br /> phit = (-(I-c1).^2+(I-c2).^2);<br /><br />endRobert Chttps://www.blogger.com/profile/17374673003716018214noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-57245632344279845582012-04-02T12:08:55.219-07:002012-04-02T12:08:55.219-07:00% Perform a simplified version of Chan-Vese segmen...% Perform a simplified version of Chan-Vese segmentation algorithm, as<br />% described in "Solving Chan-Vese..." paper by He & Osher<br /><br />function phi = SimpleCVsegment(I,phi0,dt,numIts,epsilon)<br /><br /> function f = myFunc(t,y)<br /> f = PhiT(y,reshape(I,numel(I),1),epsilon);<br /> end<br /> <br /> % Set up coefficients for 4th order Runge-Kutta method<br /> A = [0 0 0 0; 1/2 0 0 0; 0 1/2 0 0; 0 0 1 0];<br /> b = [1/6 1/3 1/3 1/6]';<br /> c = [0 1/2 1/2 1]';<br /><br /> % Solve segmentation problem using a fixed number of steps of <br /> [m,n] = size(phi0);<br /> phi = reshape(phi0,m*n,1);<br /> for i = 1:numIts<br /> phi = RKstep(0,phi,dt,@myFunc,A,b,c);<br /> end<br /> <br /> phi = reshape(phi,m,n);<br />endRobert Chttps://www.blogger.com/profile/17374673003716018214noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-51037859975714555762011-07-08T11:57:25.985-07:002011-07-08T11:57:25.985-07:00I dont unfortunately.I dont unfortunately.Burak Bayramlihttps://www.blogger.com/profile/02849512629200782790noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-47295573685761460302011-07-08T08:37:59.647-07:002011-07-08T08:37:59.647-07:00Do you have a file "SimpleCVsegment.m" i...Do you have a file "SimpleCVsegment.m" implementation the Gibou & Fedkiw’s ODE method, which is also written by Robert Crabdall? ThanksTruonghttps://www.blogger.com/profile/13080948477512684772noreply@blogger.comtag:blogger.com,1999:blog-2703091221672544113.post-17536784865177690652011-01-22T16:24:16.900-08:002011-01-22T16:24:16.900-08:00FUCKING SWEET DUDE!!!FUCKING SWEET DUDE!!!Unknownhttps://www.blogger.com/profile/16761188296547150145noreply@blogger.com