Ellipse detection with OpenCV

Question

I would like to detect ellipses with OpenCV for Android, using the Tutorial 2-Basic included with OpenCV 2.4.1 package as a starting point. Note that my ellipse would be a p

Answer 1

One possible solution to your problem is similar to this thread Detection of coins (and fit ellipses) on an image .

You should take a look a opencv's function fitEllipse.

Answer 2

If you already have an idea of the sizes of the ellipses that you're looking for, then try the following steps:

• Find Canny edges in the image
• Use a sliding window, the size of which is the maximum length of the major axis of ellipses you're looking for.
• Within the window, collect all edge pixels, pick 6 pixels randomly and use linear least squares to fit an ellipse in the general form.
• Repeat the above step in a RANSAC like procedure.
• If there are enough inliers, you have an ellipse.

Answer 3

The parameters used in HoughCircles play a fundamental role. HoughCircles will detect not just perfect, but also near-perfect circles (ellipses). I suggest you check this examples:

• How to detect circles (coins) in a photo
• Simple object detection using OpenCV
• OpenCV dot target detection
• Reshaping noisy coin into a circle form

And this answer has a decent collection of references.