detecting rectangle in real images

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shdrone
shdrone 2014-6-17
编辑： DGM 2023-2-14
Hey all,
I want to detect and track rectangle pattern . these pattern I want to set on object which moving and captured using webcam.
So, the image will include real-world scene also - not only the pattern.
example of pattern:
I want to be able to detect the 4 corners of the white rectangle.
what about if I have black rectangle?
Thanks in advance
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shdrone
shdrone 2014-6-17
ok - no problem.
here's an image :
thanks
shdrone
shdrone 2014-6-18
Do you have a solution for this image?

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回答（4 个）

Image Analyst
Image Analyst 2014-6-18
Does the clutter have to be in the background? It requires a more time consuming and complicated algorithm. I'd take the green channel, threshold for dark things. Find objects in a certain size range with a certain Euler number. Then call bwboundaries() and take the inner boundary.
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shdrone
shdrone 2014-6-18
Hi,
I found this : http://www.mathworks.com/matlabcentral/answers/uploaded_files/8433/shape_recognition.m
I think it's working good (I tested some images).
my question : can this code give me the coordinates of the 4 corners of the rectangle or just the Centroid?
Thanks for your help
Image Analyst
Image Analyst 2016-5-21
No it can't (and that's my code so I should know). But I have an updated demo, attached, that can.

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Spandan Tiwari
Spandan Tiwari 2014-6-19
If your rectangle does not change orientation, you can try using normxcorr2 (in Image Processing Toolbox) with the rectangle as the template. If changes in orientation are possible you may have to use more than one templates.
Elizabeth Rocha
Elizabeth Rocha 2016-5-21
编辑：DGM 2023-2-14
my code for this is :
imagen=imread('img18.jpg');
recorte=imagen(112:221,218:274);
recorte2=imagen(261:309,233:317);
recorte=im2bw(recorte);
recorte2=im2bw(recorte2);
subplot(1,3,1),imshow(imagen)
rectangle('position',[218,112,56,109]);
% ---this is for captured using webcam
rectangle('position',[233,261,84,48]);
subplot(1,3,2),imshow(recorte)
subplot(1,3,3),imshow(recorte2)
if recorte==true
x=1
else
x=0
end
if recorte2==true
y=1
else
y=0
end
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Image Analyst
Image Analyst 2021-4-20
@Ayush singhal, try rectpuls() if you have the Signal Processing Toolbox. Otherwise create one pulse using ones() and zeros() and then replicate it as many times as you want with repmat.
Ayush singhal
Ayush singhal 2021-4-21
But I need stripes as a image not like pulses. stripes like black white black white black white.....
I think this needs image processing tool.

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Matt J
Matt J 2021-4-20
编辑：Matt J 2021-4-20
Ran in:
This works for the one given image. I would need more examples to see if it's a reliable solution. It uses the FEX contribution pgonCorners which must be Downloaded.
load Image
C=bwpropfilt(all(Image<50,3),'ConvexArea',1);
D=bwareafilt( bwconvhull(C)-C>0.5 ,1);
xy=fliplr(pgonCorners(D,4)); %corner coordinates
imshow(Image);
hold on
scatter(xy(:,1), xy(:,2),30,'r','filled')
hold off

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