Region Growing

This method gets image and threshold as arugments and gets the mouse click coordinates as the seed to proceed. Here, starting from the seed the intensity values of each pixel is compared with its neighbours and if it is within the threshold, it'll be marked as one.

Matlab Code

function regionGrowing(name,T)
    im=rgb2gray(imread(name));
    im=im2double(im);
    [r,c]=size(im);
    A=zeros(r,c); % segmented mask
    F=[]; % frontier list
    subplot(1,2,1);
    imshow(im);
    title('Original');
    s=uint16(ginput(1));    % get the click coordinates
    s=[s(2),s(1)];      % [row,col]
    A(s(1),s(2))=1;
    F=[F;s];
    while(~isempty(F)) % if frontier is empty
        n=neighbours(F(1,1),F(1,2),r,c);   % 4 neighbourhood
        for i=1:size(n,1)
            if(abs(im(F(1,1),F(1,2))-im(n(i,1),n(i,2)))<T && A(n(i,1),n(i,2))~=1)% less than threshold & not already segmented
                A(n(i,1),n(i,2))=1;
                F=[F;n(i,1),n(i,2)];
            end
        end
        F(1,:)=[];
    end
    subplot(1,2,2);
    imshow(A);
    title(sprintf('Threshold: %0.4f',T));
end

function out=neighbours(s1,s2,r,c)
    out=[];
    if(s2>1),  out=[out;s1,s2-1];   end
    if(s1>1),  out=[out;s1-1,s2];   end
    if(s1<r),  out=[out;s1+1,s2];   end
    if(s2<c),  out=[out;s1,s2+1];   end
end

Output

The segmented region is shown in white.