# detect square in image

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Abdul 2011 年 12 月 29 日
コメント済み: Dmitry Surov 2020 年 9 月 16 日 17:31
i want to detect square shape only in image. how can i do this using matlab?

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### 採用された回答

Chandra Kurniawan 2011 年 12 月 29 日
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.
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?

#### 3 件のコメント

Abdul 2012 年 1 月 3 日
yes, thanks a lot. how about detecting circle in image?
An Hoang 2018 年 4 月 9 日
thank you so much! How to determine whether a check box option is selected
Dmitry Surov 2020 年 9 月 16 日 17:31
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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### その他の回答 (2 件)

Sean de Wolski 2011 年 12 月 29 日
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.

#### 0 件のコメント

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Naz 2011 年 12 月 29 日

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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