Hand Detection

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I am trying to detect hand using opencv and c++.

I am able to find the contour of the hand(Positive image)with person hand present in the image.Basically I am finding largest contour and consider it as hand contour.Lets say in the given image the hand is not present then i will take any contour and consider it as the hand.

So I started thinking can I use the haar cascade to determine the rectangle of the hand and focus on that area,but I tried searching online for the xml but I think it is not available like face detection.

So given a image how can I determine from the set of contour which one is of hand?