A display driver includes a memory, a receiver, an image output unit, a controller, and an image mode selection unit. The memory stores a video signal. The receiver receives the video signal and a first control signal from a host processor, where the first control signal corresponds to the video signal. The image output unit processes the video signal stored in the memory and outputs the processed video signal to a display unit. The controller controls the image output unit based on an image mode to display an image corresponding to the video signal. The image mode selection unit detects the first control signal and a second control signal from the controller, and changes the image mode based on the first control signal and second control signal.