Azzera filtri
Azzera filtri

detect square in image

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Abdul il 29 Dic 2011
Commentato: Dmitry Surov il 16 Set 2020
i want to detect square shape only in image. how can i do this using matlab?

Risposta accettata

Chandra Kurniawan
Chandra Kurniawan il 29 Dic 2011
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;
And the result :
Is this what you need?
  3 Commenti
An Hoang
An Hoang il 9 Apr 2018
Modificato: An Hoang il 9 Apr 2018
thank you so much! How to determine whether a check box option is selected
Dmitry Surov
Dmitry Surov il 16 Set 2020
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

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Più risposte (2)

Sean de Wolski
Sean de Wolski il 29 Dic 2011
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 il 29 Dic 2011
Modificato: John Kelly il 14 Nov 2013
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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