detect square in image

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Abdul
Abdul 2011-12-29
评论： Dmitry Surov 2020-9-16
i want to detect square shape only in image. how can i do this using matlab?

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Chandra Kurniawan
Chandra Kurniawan 2011-12-29
Hello,
Is your goal only to detect square in this picture?
If so, you don't need to do shape recognition, etc.
You just need to perform some morphologichal operations only.
I = imread('3617ca70.png');
Ibw = ~im2bw(I,graythresh(I));
Ifill = imfill(Ibw,'holes');
Iarea = bwareaopen(Ifill,100);
Ifinal = bwlabel(Iarea);
stat = regionprops(Ifinal,'boundingbox');
imshow(I); hold on;
for cnt = 1 : numel(stat)
bb = stat(cnt).BoundingBox;
rectangle('position',bb,'edgecolor','r','linewidth',2);
end
And the result :
Is this what you need?
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An Hoang
An Hoang 2018-4-9
编辑：An Hoang 2018-4-9
thank you so much! How to determine whether a check box option is selected
Dmitry Surov
Dmitry Surov 2020-9-16
Can you please explain what do we get in stat variable ? It's something related to border line of each square, but i misunderstand what that means
Thanks

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更多回答（2 个）

Sean de Wolski
Sean de Wolski 2011-12-29
Those squares are very well defined.
  • Set a less than threshold to make the dark colors true and everything else false. ( BW = I<thresh )
  • Perform a connected components analysis ( doc bwconncomp)
  • Then regionprops with EulerNumber specified.
  • Apply a threshold to the regions matching the EulerNumber ( idx = [stats(:).EulerNumber] == x ) of a sample square.
  • Build a new matrix of false. ( BWnew = false(CC.ImageSize))
  • Set the indices in the connected components analysis corresponding to the matching EulerNumber to true. ( BWnew(vertcat(CC.PixelIdxList{idx})) = true)
In theory you'll have a mask of the boxes.
Naz
Naz 2011-12-29
编辑：John Kelly 2013-11-14
I just thought of an alternative idea. Instead of detecting a square, you should register the image (filled form) of interest with the raw image. Then, since you know the coordinates of each square, you can just check the pixels at those coordinates for the white/black values.

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