find out that contour is convex or not

I xave “x” contour and “o” contour for smal x-o game, and try to figure out when i got x and when o. I try it with cvConvexHull and cvConvexityDefects but stuck around for a while. Any help, any sugesstions? Mby another idea how to detect x or o? I hawe only one single out contour (x or o) in my pic and need to know witch is it.
Thanks!

hi, assuming you have a blank page and either an X or O on that page, and you want to work out which one is which through openCV… you could look for contours with holes in them (its a bool parameter you pass into findContours function).
so, O will return 2 blobs because it finds the contour for the outside of the O and the inside. the X will only return one blob since the character doesn’t have any holes inside it.