Beam projectors are widely used for large screen displays due to their high image quality at relatively low cost. Recently many works have been published extending the application area of beam projectors by employing nonideal screens such as walls and ceilings. When the color of the nonconventional screen is not white, reflected color is shifted from the original. Therefore, we need to compensate for the color distortion. Past work has been limited to global gamut mapping where the mapping function is constant over a given color screen. The represented color range is the intersection of gamuts of various colored screen areas, which limits the usable gamut severely. We propose to use adaptive mapping function which depends on the screen color and the input image of each pixel. The proposed method attempts to employ the gamut at each screen position with a constraint that the mapping function changes smoothly over the screen to avoid abrupt color variation. Experiments with natural images show that our proposed method expands the gamut and enhances the color quality significantly.