We present a beam shaping method using deformable mirrors without using a target beam shape. The key to the method is the use of an image-based metric on the quality of beam with respect to the desired attributes of the super-Gaussian output beam. This technique iteratively adjusts the deformable mirror shape to minimize the metric measured using a charge-coupled device camera. Since the algorithm does not use a target beam for the optimization, it produces the resulting super-Gaussian beam geometry consistent with the constraints imposed by the limited stroke and the finite number of actuators of the deformable mirror.