How to use imfill() function to fill the interior of the boundary surface using Matlab?

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M.S. Khan 2021-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/769527-how-to-use-imfill-function-to-fill-the-interior-of-the-boundary-surface-using-matlab

评论： M.S. Khan 2021-3-20

采纳的回答： Image Analyst

Boundary_closed_1s_3s.txt

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Hi dear community members,

i am using flood fill operation to fill the interior. i have closed the boundary surface. There are no holes on the boundary surface but still, the interior cannot be filled.

I am using the following code. Please guide me where i am making mistake. The matrix A as a text file is already attached.

Regards.

interior_filled = imfill(A,'holes')

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M.S. Khan 2021-3-12

Is the imfill() function is not capable to fill the interior region? How come, boundary surface is closed and imfill() function is not applicable?

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Answer 1

Image Analyst 2021-3-12

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https://ww2.mathworks.cn/matlabcentral/answers/769527-how-to-use-imfill-function-to-fill-the-interior-of-the-boundary-surface-using-matlab#answer_646343

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@M.S. Khan, try this:

% Demo by Image Analyst, March, 2021.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
fprintf('Beginning to run %s.m ...\n', mfilename);
grayImage = importdata('Boundary_closed_1s_3s.txt');
subplot(2, 1, 1);
imshow(grayImage, []);
impixelinfo;
axis('on', 'image');
% Create a binary image.
binaryImage = grayImage ~= 0;
% Fill the object by scanning across all columns and 
% drawing a line from the top-most pixel to the bottom-most pixel.
[rows, columns] = size(binaryImage);
for col = 1 : columns
	% Find the top most pixel.
	topRow = find(binaryImage(:, col), 1, 'first');
	if ~isempty(topRow)
		% If there is a pixel in this column, then find the lowest/bottom one.
		bottomRow = find(binaryImage(:, col), 1, 'last');
		% Fill from top to bottom.
		binaryImage(topRow : bottomRow, col) = true;
	end
end
interior_filled = binaryImage;
% interior_filled = imfill(binaryImage, 4, 'holes');
subplot(2, 1, 2);
imshow(binaryImage, []);
axis('on', 'image');
fprintf('Done running %s.m\n', mfilename);

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Image Analyst 2021-3-14

在 MATLAB Online 中打开

Here is a version that fills the interior by doing a convex hull but then erases all the little "bays" around the outside edge that got filled in "accidentally":

% Demo by Image Analyst, March, 2021.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
fprintf('Beginning to run %s.m ...\n', mfilename);
grayImage = importdata('Boundary_closed_1s_3s.txt');
subplot(2, 3, 1);
imshow(grayImage, []);
impixelinfo;
axis('on', 'image');
title('Original Image', 'FontSize', fontSize);
% Create a binary image.
binaryImage = (grayImage ~= 0);
subplot(2, 3, 2);
imshow(binaryImage, []);
axis('on', 'image');
title('Original Binary Image', 'FontSize', fontSize);
% Take the convex hull.
interior_filled = bwconvhull(binaryImage);
% interior_filled = imfill(binaryImage, 4, 'holes');
subplot(2, 3, 3);
imshow(interior_filled, []);
axis('on', 'image');
title('Convex Hull Image', 'FontSize', fontSize);
% Let's see how many blobs there are in the outer "bays".
% That is how many little nooks and crannies got filled in by doing the convex hull.
% But first there are some holes in the binary image that we need to fill (like near the top of the shape).
binaryImage = imfill(binaryImage, 'holes');
% Now find the difference between them.
filledBlobs = xor(interior_filled, binaryImage);
% Get rid of the largest blob - this is the main interior.
% Any small outerblobs, if any, will remain.
filledBlobs = filledBlobs & ~bwareafilt(filledBlobs, 1);
subplot(2, 3, 4);
imshow(filledBlobs, []);
axis('on', 'image');
caption = sprintf('Outer Blobs Mask: blobs between\nOriginal and Convex Hull');
title(caption, 'FontSize', fontSize);
% Count them.
[labeledImage, numBlobs] = bwlabel(filledBlobs);
message = sprintf('There are %d blobs between the convex hull and the binary image.\nNow let us erase them.', numBlobs);
uiwait(msgbox(message));
% Erase all those tiny blobs between the original binary image and the convex hull.
interior_filled(filledBlobs) = false;
subplot(2, 3, 5);
imshow(interior_filled, []);
axis('on', 'image');
title('Final Mask', 'FontSize', fontSize);
g = gcf;
g.WindowState = 'maximized'
fprintf('Done running %s.m\n', mfilename);

M.S. Khan 2021-3-17

在 MATLAB Online 中打开

Matrix_Boundary_fills_1s_only.txt

Using this code, i am generating the closed surface. 'P' is used to fill the gaps along the boundary surface.

Could you please guide me if we change the shape to the traingular or circular, should 'P' be changed

Aorg = load('Matrix_Boundary_fills_1s_only.txt');
gapmax = 40; 
[m,n] = size(Aorg);
A = double(Aorg>0); 
P=[1 2 3;    % used to fill the gaps. It should be readjusted to fill gaps. 
   8 0 4;
   7 6 5];
Apad = zeros(m+2,n+2);
maxattempt = 10;
for niter = 1:maxattempt  
    Apad(2:end-1,2:end-1) = A>0;
    B = zeros(m,n,8);
    for k=1:8
        [i,j] = find(P==k);
        B(:,:,k) = Apad(i-2+(2:end-1),j-2+(2:end-1));
    end
    As = A>0 & sum(diff(B(:,:,[1:8 1]),1,3)==1,3)<=1;
    [y,x] = find(As);
    if isempty(x)
        break
    end
%     p = length(x);
    xy = [x,y];
    xy1 = reshape(xy,1,[],2);
    xy2 = reshape(xy,[],1,2);
    d = sum(abs(xy1-xy2),3);
    d(d==0) = NaN;
    i = (1:size(d,1))';
    [dmin,j] = min(d,[],2);
    keep = dmin <= gapmax;
    i = i(keep);
    j = j(keep);
    for k=1:length(i)
        xyi = xy(i(k),:);
        xyj = xy(j(k),:);
        dxy = xyi-xyj;
        if abs(dxy(1)) > abs(dxy(2))
            xr = linspace(xyi(1),xyj(1),abs(dxy(1))+1);
            yr = round(interp1([xyi(1),xyj(1)],[xyi(2),xyj(2)],xr));
        else
            yr = linspace(xyi(2),xyj(2),abs(dxy(2))+1);
            xr = round(interp1([xyi(2),xyj(2)],[xyi(1),xyj(1)],yr));
        end
        A(sub2ind(size(A),yr(2:end-1),xr(2:end-1))) = 3; 
    end
end
end
dlmwrite('Boundary_closed_1s_3s.txt',A);

M.S. Khan 2021-3-19

Hi Dear Image Analyst, could you please share your feedback. I am waiting for your expert point of view. Regards!

M.S. Khan 2021-3-20

i think, the 'P' should be changed with respect to the shape of the object. i am trying how to handle it.

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How to use imfill() function to fill the interior of the boundary surface using Matlab?

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How to use imfill() function to fill the interior of the boundary surface using Matlab?

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