Abstract: A technique and system of representing a group of images, the technique includes determining the values of one or more dominant colors for the group of images and deriving a dominant color representation expressing the group of images in terms of one or more of said dominant color values. The inventive technique and system can be applied to any group of images, or image regions, including regions within image.

Abstract: A method of and an apparatus for removing a naturally grown oxide film and contaminants on the surface of a semiconductor substrate and then forming a thin film on the cleaned surface. The semiconductor substrate is placed in a pretreatment chamber and then hydrogen chloride gas is introduced into the chamber. Then, the semiconductor substrate is heated at a temperature between 200.degree..about.700.degree. C. and the surface of the semiconductor substrate is irradiated with ultraviolet rays, whereby the naturally grown oxide film and other contaminants on the semiconductor substrate can be removed. Then, a thin film is formed on the cleaned surface of the semiconductor substrate by a CVD method or a sputter method. According to this method, the naturally oxide film and other contaminants can be removed from the surface of the semiconductor substrate at a low temperature and the thin film can be formed on the cleaned surface.