A display device includes: a display including a plurality of pixels; and a controller configured to: receive an external input image signal, adjust the external input image signal to compensate for brightness deviations of the pixels, and transmit corresponding image data signals to the pixels, wherein the controller includes: a data input section configured to receive the external input image signal and transmit a test image data signal to the pixels through a data driver, a luminance information extracting section configured to: extract brightness information for the pixels after displaying a test image in accordance with the test image data signal, and calculate first, second, and third parameters, using the brightness information, and a data compensating section configured to generate the image data signals by adjusting the external input image signal based on the first, second, and third parameters.