Outer and inner contour of the image from the centroid

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Ivan Shorokhov 2015-1-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168951-outer-and-inner-contour-of-the-image-from-the-centroid

评论： Image Analyst 2015-1-5

采纳的回答： Image Analyst

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Hello everybody,

I have following image:

 I would like to find the Outer and inner contour of the image from the centroid, for example as here:

I would appreciate any help!

Thanks in advance!

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Answer 1

Image Analyst 2015-1-5

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https://ww2.mathworks.cn/matlabcentral/answers/168951-outer-and-inner-contour-of-the-image-from-the-centroid#answer_164014

Use bwconvhull() and then bwboundaries(). The outer is the boundaries of the convex hull. To get the inner, subtract or XOR the original from the convex hull, then call bwboundaries().

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Ivan Shorokhov 2015-1-5

编辑：Ivan Shorokhov 2015-1-5

在 MATLAB Online 中打开

Dear Image Analyst,

I have tried to implement your answer, but it didn't work, could you show me please how to do it right.

Here is the result and code:

close all; clc; clear all;
original=imread('LA_shape.jpg');
original = rgb2gray(original);
figure; imshow(original);
outer = bwconvhull(original,'objects',4);
subplot(2,2,1);imshow(outer);
B = bwboundaries(outer,'noholes');
subplot(2,2,2); imshow(outer);
for k=1:length(B),
    boundary = B{k};
    hold on;
    plot(boundary(:,2), boundary(:,1));
end
inner = im2bw(original)- outer;
B2 = bwboundaries(inner,'noholes');
subplot(2,2,3);imshow(inner);
for l=1:length(B2),
    boundary1 = B2{l};
    hold on;
    plot(boundary1(:,2), boundary1(:,1),'r');
end
hold off;
subplot(2,2,4); imshow(original);
hold on; 
for l=1:length(B2),
    boundary1 = B2{l};
    plot(boundary1(:,2), boundary1(:,1),'r');
end
for k=1:length(B),
    boundary = B{k};
    plot(boundary(:,2), boundary(:,1));
end