This paper deals with visual servoing for 6-degree-of-freedom robot manipulators, and considers the problem of establishing whether and how it is possible to reach the desired location while keeping all features in the field of view and following a straight line in the Euclidean space. A path-planning technique based on a parametrization of the camera path through polynomials is proposed, which overcomes existing methods dealing with this problem. The generated image trajectory can be tracked by using an image-based visual servoing controller.