I am wondering how to check if the user is performing gesture on our predefined area. I have an criteria and that is , let suppose , If I have a transparent graphics of word "B" on the screen , then user should start filling it with color with gesture (with the touch of his finger). he starts it with the below corner of the B and end up how we write the b when writing with the pencil.
So how to achieve this type of gesture and how to just restrict user to use the gesture on on that part of the screen ? please any idea about it or share me any thing which is similar to it.