How to retrieve the centroid and angle of an ellipse drawn on an image in a gui?

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Nisha Bharti on 7 Jun 2016

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Answered: Image Analyst on 7 Jun 2016

I want to create an interactive ellipse on an image in a gui and retrieve its poperties like semi-major axis,semi-minor axis, angle and centroid for the same. I am struck at this. Using imellipse, I am not able to get the centroid and the angle. I have to get these values in a structure and then generate a xml file of it. Thanks!

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Answer 1

Matt J on 7 Jun 2016

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https://au.mathworks.com/matlabcentral/answers/288199-how-to-retrieve-the-centroid-and-angle-of-an-ellipse-drawn-on-an-image-in-a-gui#answer_224704

ellipsefit.m

If you have a well-distributed set of points on the ellipse, you can use the attached file to fit the points. The output gives all the ellipse parameters that you mentioned.

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Nisha Bharti on 7 Jun 2016

It's giving this error:

Attempted to access XY(2,:); index out of bounds because numel(XY)=1.

Error in ellipsefit (line 6) Y=XY(2,:).' - cxy(2);

Matt J on 7 Jun 2016

Edited: Matt J on 7 Jun 2016

The error means that you have called ellipsefit(XY) with a scalar value for XY. The expectation is that XY is a 2xN matrix whose columns are N points on the ellipse.

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