1. A method of displaying a zoomed version of stored image on a display, where the stored image is defined by a set of data entries mapped to respective pixels of the display, the method comprising the steps of: (1) scaling the stored image relative to the display in accordance with a desired zooming ratio; (2) locating the scaled image at an initial position relative to the display; (3) determining the extent to which each display pixel is overlapped by features of the scaled image, and assigning to each display pixel a corresponding colour tone; (4) shifting the scaled image relative to said initial position one or more times and, for the or each shift, repeating step; and (5) cyclically displaying each of the sets of assigned colour tones in turn for as long as the zoomed version is to be displayed.