1. A method for controlling a display device, the method comprising: receiving a signal including video data and supplementary information, the supplementary information including text data, position information of the text data relative to the video data, and size information of the text data; displaying the received signal so that the text data overlaps the video data according to the position information and the size information; detecting color information of the text data; selecting a portion of the video data based on the position information and the size information; detecting color information of the selected portion; determining a color difference between the video data and the text data included in the received signal, based on the detected color information of the text data and the detected color information of the selected portion; comparing the determined color difference with at least one reference value; and controlling a display characteristic of the text data depending on a result of said comparing, said text data display characteristic controlling comprising only one of: controlling the color difference between the text data and the video data by controlling a color of the displayed text data; and controlling a luminance of the displayed text data.
1. A method for controlling a display device, the method comprising: receiving a signal including video data and supplementary information, the supplementary information including text data, position information of the text data relative to the video data, and size information of the text data; displaying the received signal so that the text data overlaps the video data according to the position information and the size information; detecting color information of the text data; selecting a portion of the video data based on the position information and the size information; detecting color information of the selected portion; determining a color difference between the video data and the text data included in the received signal, based on the detected color information of the text data and the detected color information of the selected portion; comparing the determined color difference with at least one reference value; and controlling a display characteristic of the text data depending on a result of said comparing, said text data display characteristic controlling comprising only one of: controlling the color difference between the text data and the video data by controlling a color of the displayed text data; and controlling a luminance of the displayed text data. 2. The method according to claim 1 , wherein the detecting color information of the selected portion comprises calculating an average value of colors of respective pixels corresponding to the selected portion.