Asked by Aon
on 14 Sep 2018

In a multi-line binary image with different slopes and center points. How do you find the coordinate where most lines intersect? (it should be close where the red arrow points)

Thanks in advance

Answer by jonas
on 14 Sep 2018

Edited by jonas
on 15 Sep 2018

Accepted Answer

A good solution would be to identify each line by e.g. Hough transform, determine each intersection (e.g. InterX ) and then find the cluster with the highest density of intersections using e.g hist3.

In this case, it seems the point of interest is also the point with the highest density of white pixels, so you could apply some smoothing filter and then find the highest value in the matrix. Here's an example using a very simple 10x10 pixel average.

w=ones(10,10);

A=conv2(I,w/numel(w),'same')

imagesc(A)

colormap(gca,'jet')

jonas
on 15 Sep 2018

Nice! You could put the intersections in a binary matrix, smooth it and find the highest value in the resulting matrix, just like I did in the original answer.

Better yet, use hist3 to find the bin with highest density of points. Something like

[count,bin]=hist3([x,y],'cdatamode','auto');

[idx,idy]=find(count==max(count(:)));

xmax=bin{1}(idx);

ymax=bin{2}(idy);

and adjust the bin size to get the desired resolution.

Aon
on 16 Sep 2018

hist3 worked very well! Thank you very much for the help.

jonas
on 16 Sep 2018

Nice! My pleasure

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Answer by Image Analyst
on 15 Sep 2018

Have you considered dbscan?

MATLAB Code for it:

Aon
on 16 Sep 2018

hist3 helped me very well but I will read more about dbscan also. Thank you!

Image Analyst
on 16 Sep 2018

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