finding endpoints of a label
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Hi, I have the following matrix. I =
0 0 0 0
0 1 1 1
0 0 0 0
0 0 0 0
0 0 1 0
0 0 1 0
0 0 1 0
[B,L,N,A]=bwboundaries(I,'noholes');
L =
0 0 0 0
0 1 1 1
0 0 0 0
0 0 0 0
0 0 2 0
0 0 2 0
0 0 2 0
idx=find(L==1) endpoints of label 1 are (2,2) and (2,4)
I need to find that endpoints similarly in case of label 2. Thanks endpoints of label 1 are (2,2) and (2,4)
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Akzeptierte Antwort
Oleg Komarov
am 26 Jun. 2011
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
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Weitere Antworten (2)
Walter Roberson
am 26 Jun. 2011
B = bwboundaries(I,'noholes');
xy_1_first = B{1}(1,:);
xy_1_last = B{1}(end,:);
xy_2_first = B{2}(1,:);
xy_2_last = B{2}(end,:);
Andrei Bobrov
am 27 Jun. 2011
L = bwlabel(I)
I2 = bwmorph(I,'endpoints')
epout = arrayfun(@(i1)find(I2 & L == i1)',1:max(L(:)),'un',0)
example:
I =
0 1 0 1 1 1
1 1 0 0 0 1
1 0 0 0 0 0
1 0 1 1 1 0
0 0 1 0 0 0
0 0 1 0 1 1
0 0 1 0 0 0
0 0 0 0 0 0
1 1 0 0 1 0
0 1 1 0 1 0
0 0 1 0 1 0
0 0 1 0 1 0
0 1 1 0 1 0
0 1 0 0 0 0
0 1 0 1 0 0
0 1 1 1 0 0
0 0 0 0 0 0
>> L = bwlabel(I)
I2 = bwmorph(I,'endpoints');
epout = arrayfun(@(i1)find(I2 & L == i1)',1:max(L(:)),'un',0);
L =
0 1 0 4 4 4
1 1 0 0 0 4
1 0 0 0 0 0
1 0 3 3 3 0
0 0 3 0 0 0
0 0 3 0 5 5
0 0 3 0 0 0
0 0 0 0 0 0
2 2 0 0 6 0
0 2 2 0 6 0
0 0 2 0 6 0
0 0 2 0 6 0
0 2 2 0 6 0
0 2 0 0 0 0
0 2 0 2 0 0
0 2 2 2 0 0
0 0 0 0 0 0
>> epout{5}
ans =
74 91
>>
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