1. A method for transforming a display image on a mobile device from a first orientation to a second orientation, the mobile device comprising a main memory, a cache having a predetermined size and a display buffer, the method comprising the steps of: a) breaking up the display image into n sub-images, wherein n is the smallest possible integer for which the size of the image, divided by n, is less than the size of the cache; and b) transforming each of said sub-images individually, said transforming step including selecting a pixel of a sub-image stored in the cache, determining a transformed location for said pixel in the display buffer, and writing the pixel to the display buffer at the determined location.