In order to display an image in a display device, in which a plurality of sub pixels within a unit pixel receives driving power from one driving power line, a driving voltage stability weak pattern is detected by analyzing image data. When the input image is determined as the driving voltage stability weak pattern, a white balance correction gain of each sub pixel is decreased while a ratio among the white balance correction gains of the sub pixels is maintained. Target luminance for displaying the input image is changed. A voltage level of the driving power is change in accordance with the changed target luminance.