1. A display device comprising: a similar gray level block detector configured to detect a pixel data block in which a gray level difference between a plurality of pixel data included in an image signal is smaller than or equal to a threshold; a skin tone detector configured to detect the pixel data block including a skin tone; and a gamma processor configured to apply a first gamma to a plurality of pixel data included in the pixel data block when the pixel data block does not include the skin tone and apply a second gamma to the plurality of pixel data included in the pixel data block when the pixel data block includes the skin tone.