1. A method of controlling brightness of a user-selected area on a monitor screen, the method comprising the steps of: determining a starting point of a topmost image line of a displayed image as a new reference point; detecting a line pattern included in one of image lines of said displayed image, said pattern including an indicator whose ends are horizontally aligned with vertical edges of said user-selected area; measuring horizontal distances of said vertical edges with respect to said reference point; identifying a highlight area by calculating horizontal coordinates of said highlight area from said measured horizontal distances; and amplifying a brightness gain of said identified highlight area.