How to detect corners of irregular binary shape?

Question

Mathias Smeets 2022-7-28

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1769730-how-to-detect-corners-of-irregular-binary-shape

评论： Mathias Smeets 2022-7-29

I have a lot of binary images similar like this:

Now I want to detect the 4 corners of this (almost) rectangle. It is however important these corners are detected always at the same place and do not change when my image changes a little bit. (I am detecting a sample that undergoes some forces so the images change slightly over time). So for example at the top right, I do not want my detection to switch constantly between these two possible edge points. I just want to detect the highest possible edge point at the 4 corners.

Methods I have tried:

Calculate all edges with function edge and then calculate the points closest to the corners of the entire image. This will however give the problem of not having a constant corner point, like I already explained.
Take the corners of the uppermost (and lowermost) row. This will give points somewhere in the middle because the shape is a little curved at the top.

I am honestly really stuck and help would be greatly appreciated!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2022-7-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1769730-how-to-detect-corners-of-irregular-binary-shape#answer_1017550

编辑：Matt J 2022-7-29

在 MATLAB Online 中打开

You might try pgonCorners from the File Exchange:

https://www.mathworks.com/matlabcentral/fileexchange/74181-find-vertices-in-image-of-convex-polygon?s_tid=srchtitle

figure

runIt(load('BWimage1').BW);

figure

runIt(load('BWimage400').BW);

function [X,Y]=runIt(BW)

V=pgonCorners(BW,8);

[I,J]=deal(V(:,1), V(:,2));

[~,top2]=mink(I,2);

[~,bottom2]=maxk(I,2);

X=J([top2;bottom2]); Y=I([top2;bottom2]);

imshow(BW); hold on

scatter(X,Y,'filled','MarkerFaceColor','r','SizeData',80); hold off

end

4 个评论
显示 2更早的评论隐藏 2更早的评论

Matt J 2022-7-29

在 MATLAB Online 中打开

I think uniquetol should fix that, e.g.,

V=uniquetol( pgonCorners(BW,8) ,3,'DataScale',1,'ByRows',true) ;

Mathias Smeets 2022-7-29

This works perfectly, thank you!

请先登录，再进行评论。

Answer 2

Image Analyst 2022-7-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1769730-how-to-detect-corners-of-irregular-binary-shape#answer_1017000

在 MATLAB Online 中打开

If the points are always supposed to be at the same place, just define them. Then, if the image is not true there, then find the distance of all points in the blob to the defined location and select the blob point that is closest to the defined reference point.

% Define expected corner point locations.
refRow = 20;
refCol = 50; % Whatever.
% Now the blob may not exist at that location so find out what locations it exists at.
[r, c] = find(mask);
% Find distances from reference point to all points in the blob.
distances = sqrt((refRow - r) .^ 2 + (refCol - c) .^ 2);
% Find the minimum distance, which will be the distance of the ref point to
% the closest point that is actually in the blob.
[minDistance, index] = min(distances)
% Get the location of the point on the blob closest to the reference point.
actualRow = r(index)
actualCol = c(index)

5 个评论
显示 3更早的评论隐藏 3更早的评论

Image Analyst 2022-7-29

I had a similar situation and to solve it I had to manually mark about a hundred images and then use Deep Learning to predict where the points should be.

Mathias Smeets 2022-7-29

Thank you for your answer, I am very close to solving the problem with Matt J his answer.

However, I am very interested in learning things about deep learning for similar problems regarding image detection. Since you seem an expert, do you have any suggestions where to learn working with deep learning software? Do you do this in MATLAB?

请先登录，再进行评论。