We consider an optimization problem arising in the design of controllers for OLED displays. Our objective is to minimize the amplitude of the electrical current flowing through the diodes which has a direct impact on the lifetime of such a display. The optimization problem consist of finding a decomposition of an image into subframes with special structural properties that allow the display driver to lower the stress on the diodes. For monochrome images, we present an algorithm that finds an optimal solution of this problem in quadratic time. Since we have to find a good solution in realtime, we consider an online version of the problem in which we have to take a decision for one row based on a constant number of rows in the lookahead. In this framework this algorithm has a tight competitive ratio. A generalization of this algorithm computes near optimal solutions of real-world instances in realtime. © Springer-Verlag Berlin Heidelberg 2007.