This paper proposes a new approach to control a flow. Controlling a flow consists either to change its state to another state or to maintain its current state whatever external disturbances. Here the control of the laminar plane Poiseuille flow is considered. To estimate the state of this flow, existing control methods rely on a set of limited wall shear stress measurements. These existing methods suffer from limited observations, from noisy measurements and from the initialization involved in the observer required to estimate the flow state. To deal with these issues, this paper proposes a vision-based control approach. More precisely, by visualizing a fluid flow, dense flow velocity maps can be computed via optical flow techniques and subsequently used to build an observer-free closed-loop control law. This approach is formally proven to be of great improvements for the control of this flow in comparison with existing control approaches.