Image processing of a binary image

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Shubham
Shubham on 21 Feb 2023
Edited: Shubham on 27 Feb 2023
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.
  5 Comments
Shubham
Shubham on 21 Feb 2023
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
Jan on 21 Feb 2023
"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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Accepted Answer

Jan
Jan on 21 Feb 2023
Edited: Jan on 21 Feb 2023
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
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.
  5 Comments
Jan
Jan on 22 Feb 2023
Do you have some example code, which creates random ellipses?
Shubham
Shubham on 23 Feb 2023
Edited: Shubham on 24 Feb 2023
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.

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More Answers (2)

Image Analyst
Image Analyst on 22 Feb 2023
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.
  1 Comment
Matt J
Matt J on 22 Feb 2023
Edited: Matt J on 22 Feb 2023
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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Matt J
Matt J on 21 Feb 2023
Edited: Matt J on 21 Feb 2023
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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