![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/511772/image.png)
how to change the interior pixel of a closed boundary surface to a different pixel using MATLAB?
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I have a closed boundary surface of an object. i want to fill the interior which is already zero. How can i change the zero to any other digit so that i can do some mathematical operations. Regards for all cooperation of community members.
i have used the following code to handle it but i couldnt figure out.
A = load('Boundary_closed_1s_3s.txt')
Perimeter=bwperim(A)
interior_filled = imfill(A,'holes')
A = 3*double(A)
interior_filled = 2*double(interior_filled)
interior_filled(Perimeter)=A(Perimeter)
The above code is giving me the closed boundary surface? Could anyone guide me how to replace the interior that is already filled as zero but i want to repalce with another number number like 2.
Thanks for all guidance in advance.
1 Comment
Image Analyst
on 7 Feb 2021
The shape is not closed. See the apex at the left. Do you want to close it, like with bwconvhull()?
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/511772/image.png)
Accepted Answer
Image Analyst
on 7 Feb 2021
The shape is not closed but you can close it with bwconvhull() if you're okay with the shape being a convex shape, like your rectangle.
A = load('Boundary_closed_1s_3s.txt');
A = logical(A);
subplot(2, 1, 1);
imshow(A);
interior_filled = bwconvhull(A);
subplot(2, 1, 2);
imshow(interior_filled);
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/511777/image.png)
More Answers (4)
KSSV
on 4 Feb 2021
Yopu can exclude the boundaries by indexing right?
A = interior_filled(2:end-2,2:end-2) ;
Now you apply the given values as you have tried on A.
Walter Roberson
on 5 Feb 2021
fill the holes. subtract the original, and what is left will be the interiors. Multiply by constant and add to the original.
yanqi liu
on 5 Feb 2021
clear all; clc; close all;
A = load('Boundary_closed_1s_3s.txt');
b = im2bw(A);
b = imclose(b, strel('disk', 3));
b2 = imfill(b, 'holes');
b3 = logical(b2 - b);
A2 = im2uint8(mat2gray(A));
A2(b3) = 128;
figure;
imshowpair(A,A2,'montage');
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/510032/image.png)
please use different value, such as 64,100,128,……
yanqi liu
on 5 Feb 2021
sir,may be use the follow code
clear all; clc; close all;
A = load('Boundary_closed_1s_3s.txt');
b = im2bw(A);
b = imclose(b, strel('line', 3, -45));
b2 = imfill(b, 'holes');
b3 = logical(b2 - b);
A2 = im2uint8(mat2gray(A));
A2(b) = 0;
A2(b3) = 128;
figure;
imshowpair(A,A2,'montage');
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/510212/image.png)
2 Comments
yanqi liu
on 7 Feb 2021
the reason is
at the sharp corner on the left, there is a gap that needs to be filled. may be can zoom in to check
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