A method of mapping a four primary input signal to sets of four sub-pixels of a display device, the method including sub-sampling the input samples of the four primary input signal by assigning the first, second and third input signals of a particular input sample to the first, second and third sub-pixels, producing first, second and third primary colors of a particular set of four adjacent sub-pixels, respectively, and the fourth input signal of a further input sample to the fourth sub-pixel, producing a fourth color of said particular set of the four adjacent sub-pixels, wherein the particular input sample and the further input sample are associated with adjacent positions on the display device.