Question

I am trying to detect ellipse in an image using opencv. I find the contours which include ellipse and also some other ones.

Any suggestions that how can I check which contours are ellipse?

Answer 1

if I understand you correctly, you have detected contours some of them are ellipses and some are not and you want to be able to decide which ones are. Is it right?
If yes, I would suggest to use cv::fitEllipse(). The doc says that it fits an ellipse to a vector of points so that R-squared is minimal. Unfortunately, the function does not return explicitly the R-squared value. You can maybe implement it yourself…

As a workaround, you can also use a something such as:

1. Get the contour C
2. Fit an ellipse E to C
3. Compare E to C.

To compare them you can use moments (cf. cv::moments() and cv::matchShapes()).
I do not think you need invariant moments here, though.

Alternatively, you can draw C and E find what proportion of there surface overlap.

Good luck,