1. A method of gaze estimation, the method comprising: converting at least an eye image of a viewer watching at least a video image displayed on a screen into at least a heat map; detecting at least a location of a centre of at least an eye on the at least a heat map; converting the detected at least a location of the centre of the at least an eye into at least a first position of the gaze of the viewer on said screen by using a mapping function based on centre-bias property of human gaze distribution.