1. A method for converting an image for displaying on a display surface, comprising the steps of: scaling an input image to generate a foreground image, in which a content of the foreground image corresponds directly to a content of the input image, and in which a resolution of the foreground image when displayed is smaller than a resolution of a display surface; transforming the input image to a background image, in which a content of the background image depends indirectly on the input image, and in which a resolution of the background image is larger than the resolution of the foreground image; and combining the foreground image with the background image to form an output image, in which pixels of the foreground image replace corresponding pixels of the background image.