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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 perfect-photoshop one.
From what I understand, using the "HoughCircles" will only find perfect (or so) circles, thus leaving ellipses out.
Any help would be much appreciated as I am a total beginner at OpenCV
This is what I've tried so far
case Sample2NativeCamera.VIEW_MODE_CANNY: (ignore the Canny mode...)
capture.retrieve(mGray, Highgui.CV_CAP_ANDROID_GREY_FRAME);
Imgproc.HoughCircles(mGray, mCircles, Imgproc.CV_HOUGH_GRADIENT, 1, 20);
Log.d("Ellipse Points", " X " + mCircles.get(1,1)[0] + mCircles.get(1, 1)[1]);
break;
If you think any more info could be useful, please let me know.
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To identify circles, ellipses, or in general, any shape in which the pixels are connected we use the SimpleBlobDetector() function of OpenCV.
OpenCV has a bunch of pre-trained classifiers that can be used to identify objects such as trees, number plates, faces, eyes, etc. We can use any of these classifiers to detect the object as per our need.
Blob stands for Binary Large Object and refers to the connected pixel in the binary image. The term "Large" focuses on the object of a specific size, and that other "small" binary objects are usually noise.
The function cv2.approxPolyDP() approximates a contour shape to another shape with less number of vertices. It accepts the following arguments − cnt − The array of the contour points. epsilon − Maximum distance from contour to approximated contour. A wise selection of epsilon is needed to get the correct output.
If you already have an idea of the sizes of the ellipses that you're looking for, then try the following steps:
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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.
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