How to detect specific shaped objects with any different orientations in Image processing ?

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SACHIN PATEL 2018-12-26

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评论： SACHIN PATEL 2018-12-26

Hello, I want to know that how to detect the objects with different orientations using Area ratio, in which the problem is the bounding box is not oriented with the same orientation as the object, due to that the area ratio is not accurate and object with different orientation is not detected. How to rotate the bounding box also with the same angle as the object orientation....?

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KSSV 2018-12-26

Attach image and tell your expectations.

SACHIN PATEL 2018-12-26

I am not talking about specific image, but the problem is the bounding box is not oriented as the object orientation, due to which the area of oriented shape bounding box is larger. And the area ratio of Bounding box to Original object area is not the required for detection of object in image, So I thought if there is any means to create the bounding box that can be oriented also according to object orientation, then possibility of oriented object can be detected. So please help me that how can I create the bounding box with orientation of same as object orientation ?

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Answer 1

KSSV 2018-12-26

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https://ww2.mathworks.cn/matlabcentral/answers/437232-how-to-detect-specific-shaped-objects-with-any-different-orientations-in-image-processing#answer_353929

在 MATLAB Online 中打开

YOu can rotate the bounding box by using your desired angle as below:

% bounding box coordinates 
B = [ 0 0 ; 1 0 ; 1 1 ;0 1 ; 0 0]' ;
th = pi/4 ;
R = [cos(th) -sin(th) ; sin(th) cos(th)] ;
% Rotate by th 
B1 = R*(B-mean(B,2))+mean(B,2) ;
figure
hold on
patch(B(1,:),B(2,:),'r')
patch(B1(1,:),B1(2,:),'k')

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SACHIN PATEL 2018-12-26

编辑：SACHIN PATEL 2018-12-26

Thank you sir, The rotation concept is working properly for above code. But when I use regionprops function of matlab for find bounding box, how I can find the bounding box inclined itself and surrounding the object in the image. Because, the bounding box should be of appropriate size surrounding the object. If the bounding box is detected first surrounding the object, and then rotated, then the size of bounding box will not be appropriate. But I got somewhat logic and idea from your answer to rotate Bounding Box. Thank you for your time and help. Also sir I want to know the logic behind subtracting mean from B Array. and after rotation adding mean to it.

Thank you.

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