Shape Detection (circle, square, rectangle, triangle, ellipse) for a camera captured image + i OS 5 + Open CV

Question

I am new to OpenCV and need to know the method of OpenCV which detects different shapes (circle, square, rectangle, triangle, ellipse) in a camera captured image for iPhone.

Answer 1

First you will probably need to look at an edge detector such as Canny to extract the shapes into a binary image. (Although this may be expensive for the iphone)

For circles I would have a look at the HoughCircles.

For squares and rectangles you should look at the findContours method and the sample code squares.cpp in the samples directory when you downloaded opencv.

With a quick google search I was able to find an article about detecting shapes in C# which roughly corresponds to the methods you would use in another language while using the opencv library.

I have not used opencv in ios but I hope this will help get you started.