curvature direction

Question

Nithyakalyani. 2012-3-21

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https://ww2.mathworks.cn/matlabcentral/answers/32973-curvature-direction

i want to find curvature direction in a circle image.can anyone help me with matlab code to find the direction of curvature as clockwise or counterclockwise.

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Jan 2012-3-21

A circle does not have a direction. Please post a picture to explain, how the orientation could be detected.

Nithyakalyani. 2012-3-21

ridges in the fingerprint image is the image i have considered

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Answer 1

Matt Kindig 2012-3-21

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在 MATLAB Online 中打开

Is the circle actually part of an image, or do you have the coordinates of the circle? If you have the coordinates, it's just a matter of calculating the sign of the cross product.

    cp = cross( [x(2)-x(1), y(2)-y(1), 0], [x(3)-x(1), y(3)-y(1), 0])
    direction = sign(cp);  %+1 if counterclockwise, -1 if clockwise

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Matt Kindig 2012-3-21

It's not clear to me then how you define clockwise or counterclockwise in your image. Given only an image, how can you tell which direction in which?

Nithyakalyani. 2012-3-22

actually i have considered fingerprint image..i need to find the ridge curvature direction..thats why i askd dis question

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Answer 2

Matt Kindig 2012-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/32973-curvature-direction#answer_41734

It sounds like you mean you want to find the curvature itself (using a technique like shown here: http://en.wikipedia.org/wiki/Curvature. This has nothing to do with the clockwise/counterclockwise direction.

As myself and Jan Simon have requested, can you post an example of your fingerprint image? We can't make code recommendations without knowing what kind of image your are working with.

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Nithyakalyani. 2012-3-23

i dono how to post an image..kindly say me how to do dat

Jan 2012-3-23

Just search in this forum. It is explained e.g. in the "Markup help" link on this page, and at http://www.mathworks.com/matlabcentral/answers/243-how-do-i-post-a-picture-with-my-question .

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