A display apparatus comprising: a signal receiver configured to receive an image signal; a display configured to display an image; a processor configured to: identify a first pixel, a second pixel and a third pixel of the image, wherein the second pixel and the third pixel are adjacent to the first pixel, and the first pixel is between the second pixel and the third pixel, calculate a first pixel value difference between the first pixel and the second pixel and a second pixel value difference between the first pixel and the third pixel, identify an absolute difference value between the first pixel value difference and the second pixel value difference as a change degree and identify a direction from the first pixel towards one selected among the second pixel and the third pixel as a change direction, wherein the selected one is the second pixel if the first pixel value difference is smaller than the second pixel value difference, and the selected one is the third pixel if the second pixel value difference is smaller than the first pixel value difference, and identify a reference pixel and change the pixel value of the first pixel to the pixel value of the reference pixel, wherein the reference pixel is placed in the identified change direction and is away from the first pixel by a distance corresponding to the identified change degree. a signal receiver configured to receive an image signal; a display configured to display an image; a processor configured to: identify a first pixel, a second pixel and a third pixel of the image, wherein the second pixel and the third pixel are adjacent to the first pixel, and the first pixel is between the second pixel and the third pixel, calculate a first pixel value difference between the first pixel and the second pixel and a second pixel value difference between the first pixel and the third pixel, identify an absolute difference value between the first pixel value difference and the second pixel value difference as a change degree and identify a direction from the first pixel towards one selected among the second pixel and the third pixel as a change direction, wherein the selected one is the second pixel if the first pixel value difference is smaller than the second pixel value difference, and the selected one is the third pixel if the second pixel value difference is smaller than the first pixel value difference, and identify a reference pixel and change the pixel value of the first pixel to the pixel value of the reference pixel, wherein the reference pixel is placed in the identified change direction and is away from the first pixel by a distance corresponding to the identified change degree. identify a first pixel, a second pixel and a third pixel of the image, wherein the second pixel and the third pixel are adjacent to the first pixel, and the first pixel is between the second pixel and the third pixel, calculate a first pixel value difference between the first pixel and the second pixel and a second pixel value difference between the first pixel and the third pixel, identify an absolute difference value between the first pixel value difference and the second pixel value difference as a change degree and identify a direction from the first pixel towards one selected among the second pixel and the third pixel as a change direction, wherein the selected one is the second pixel if the first pixel value difference is smaller than the second pixel value difference, and the selected one is the third pixel if the second pixel value difference is smaller than the first pixel value difference, and identify a reference pixel and change the pixel value of the first pixel to the pixel value of the reference pixel, wherein the reference pixel is placed in the identified change direction and is away from the first pixel by a distance corresponding to the identified change degree.