Based on the idea of http://www.mathworks.com/matlabcentral/answers/10293-finding-neighbor-of-a-position
I = [0 0 0 0
0 1 1 1
0 0 0 0
1 0 0 0
1 0 0 1
1 0 0 1
1 1 1 1];
[L,num] = bwlabel(I,4);
sz = size(I);
InEn = zeros(num,2);
for n = 1:num
% Find initial point of connected component
InEn(n,1) = find(L == n,1,'first');
l = InEn(n,1);
co = 1;
while true
% row and col subs
[r c] = ind2sub(sz,l(co)); % c = ceil(l/4); r = mod(l,4)+ c*sz(1)
% Calculate 4-connected subs
neigh(1:4,1:2) = [r+[0;-1;+1;0] c+[-1;0;0;1]];
% Convert to positions
idx = (neigh(:,2)-1)*sz(1) + neigh(:,1);
% Keep positions in the range of L
idx = idx(ismember(idx,1:prod(sz)),:);
% Move onto next 4-connected component
co = co+1;
idx = idx(~ismember(idx, l) & L(idx) == n);
% If empty then we reached the end
if idx
l(co) = idx;
else
break
end
end
% Assign end
InEn(n,2) = l(end);
end
