Image processing of a binary image

Question

Shubham 2023-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/1916035-image-processing-of-a-binary-image

编辑： Shubham 2023-2-27

I made this binary image such that a bigger circle has non overlapping random smaller circles. How can I remove those circles those are not complete.

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Shubham 2023-2-21

在 MATLAB Online 中打开

I cannot provide the code, but I have referred this open source code. It generates random non overlapping circles and stores the centre coordinates and radius of the small circles.

https://in.mathworks.com/matlabcentral/fileexchange/25389-synthetic-microstructure-generator/

This code will generate circles in square domain after this you can run this. This will result in the image as uploaded. Now I need to remove those half circles and their stored data

% Initialize an image to hold one single big circle.
fontSize = 20;
bigCircleRadius = image_size/2; 
bigCircleImage = zeros(image_size, image_size, 'double');
[x, y] = meshgrid(1:image_size, 1:image_size);
bigCircleImage((x - image_size/2).^2 + (y - image_size/2).^2 <= bigCircleRadius.^2) = 1;
clear('x', 'y'); % Release these variables, they're not needed anymore.
% Display it in the upper left plot.
figure(2)
imshow(bigCircleImage, []);
title('Big Circle Mask', 'FontSize', fontSize);
maskedByBigCircle = bigCircleImage .* Image;
figure(3)
imshow(maskedByBigCircle);
title('Many Points Masked by Big Circle', 'FontSize', fontSize);

Shubham 2023-2-21

yes I can give this condition at the begining when it is picking random co-ordinates.

Like, if the chosen co-ordinates are at a distance greater than small circle radius from the big circle pheriphery, then that is a valid co-ordinate but how to compare this using code

Jan 2023-2-21

"how to compare this using code" - You must have some code, which prevent overlapping between the small circles already. The code to include only small circles inside a radius minus the radius of the small circle is trivial.

It would include something like: vecnorm(c - C) < bigR - smallR. As soon as you show your code, it would be very easy to insert this condition. But for posting a working answer, we have to guess, what you code is at first and rewrite it. This is not an efficient way to search for a solution.

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Answer 1

Jan 2023-2-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1916035-image-processing-of-a-binary-image#answer_1176500

编辑：Jan 2023-2-21

在 MATLAB Online 中打开

w = 300; % Image size

bigR = 140;

smallR = 15;

wantN = 40; % Number of small circles

N = 0;

center = zeros(wantN, 2); % List of centers

iter = 0;

while N < wantN

c = rand(1, 2) * w;

collide = any(vecnorm(c - center, 2, 2) < 2 * smallR) | ...

vecnorm(c - w/2, 2, 2) >= bigR - smallR; % <- This is the needed condition

if ~collide

N = N + 1;

center(N, :) = c;

end

iter = iter + 1; % Better crash than run infinitely

if iter > 1e6

error('Cannot find a valid solution');

end

img = ones(w, w, 3);

img = drawCircle(img, [w/2, w/2], bigR, [1,0,0]);

img = drawCircle(img, center, smallR, [0,1,0]);

image(img);

function img = drawCircle(img, C, R, Color)

s = size(img);

mask = (((1:s(1)).' - reshape(C(:, 1), 1, 1, [])).^2 + ...

((1:s(2)) - reshape(C(:, 2), 1, 1, [])).^2) <= R^2;

mask = any(mask, 3);

img = reshape(img, [], 3);

img(mask, 1) = Color(1);

img(mask, 2) = Color(2);

img(mask, 3) = Color(3);

img = reshape(img, s);

end

This shutgun technique is fragile: It will run into an infinite loop if wantN is too high.

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Jan 2023-2-22

Do you have some example code, which creates random ellipses?

Shubham 2023-2-23

编辑：Shubham 2023-2-24

Reference code is the one given in original post. We can have the overlapping criteria as vecnorm(c - center, 2, 2) < 2*major axis and at the boundary as vecnorm(c - w/2, 2, 2) >= bigR - major_axis.

But I dont know how to plot these ellipses.

In the code they have used a,b and orientation(using rand) to plot random ellipses.

@Jan

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Answer 2

Image Analyst 2023-2-22

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https://ww2.mathworks.cn/matlabcentral/answers/1916035-image-processing-of-a-binary-image#answer_1177690

在 MATLAB Online 中打开

circles.png

What I would have done is to get a mask of the big circle using bwconvhull, then call imclearborder

mask = imread('circles.png') > 128; % Get original binary image from a file.

subplot(1,2,1);

imshow(mask);

% Get mask

mask = ~bwconvhull(mask) | mask;

% Remove blobs at border

mask = imclearborder(mask);

subplot(1,2,2);

imshow(mask);

Note: some blobs are touching to form a dumbbell-shaped blob, and are not circular. If those touch the border, the whole irregular shape will get removed.

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Matt J 2023-2-22

编辑：Matt J 2023-2-22

在 MATLAB Online 中打开

circles.png

Note: some blobs are touching to form a dumbbell-shaped blob, and are not circular. If those touch the border, the whole irregular shape will get removed.

Here's a refinement that can fix some of that.

mask = imread('circles.png') > 128; % Get original binary image from a file.

subplot(1,2,1);

imshow(mask);

% Get mask

circ=circMask(size(mask));

se=strel('disk',4);

mask=imerode(mask,se);

circ=imdilate(~circ,se);

mask = circ|mask;

% Remove blobs at border

mask = imdilate( imclearborder(mask),se);

subplot(1,2,2);

imshow(mask);

function c=circMask(sz)

[m,n]=deal(sz(1),sz(2));

R=min(sz)/2;

[x,y]=deal((1:m)',1:n);

c=(x-mean(x)).^2+(y-mean(y)).^2<=R^2;

end

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Answer 3

Matt J 2023-2-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1916035-image-processing-of-a-binary-image#answer_1176450

编辑：Matt J 2023-2-21

在 MATLAB Online 中打开

load BWimage

BW0=BW;

BW=imerode(BW, strel('disk',3));

BW=bwpropfilt(BW,'Eccentricity',[0,0.3]);

BW=imdilate(BW, strel('disk',3));

immontage({BW0,BW},'Bord',[5,5],'Back','w')

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Image processing of a binary image

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