1. A method for zooming an image on a touch screen, the method comprising: detecting, by one or more processors, a trajectory on the screen formed by a continuous direct touching of the screen by a finger of a user, the trajectory beginning at a first point on the screen initially touched by the user and ending at a second point on the screen being currently touched by the user; ascertaining, by the one or more processors, that the screen has been touched by being pressed by the finger of the user at one point on the trajectory for at least a predetermined minimum period of time or that a direction pointed to by a tangent to the trajectory at the second point is at an angle with respect to a specified reference direction on the screen that is at least a predetermined minimum angle; and in response to the ascertaining, the one or more processors zooming-in or zooming-out an initial image on the screen in a manner determined by the trajectory.