1. A user interface unit comprising: a fetch unit configured to fetch pixels of a frame to be displayed, wherein the fetch circuitry is configured to fetch active pixels and not fetch inactive pixels, wherein the active pixels are within one or more active regions defined for the frame, and the inactive pixels are outside the one or more active regions; a scaler unit configured to: produce scaled pixels from the fetched pixels, basing each scaled pixel on a respective corresponding set of pixels, and output the scaled pixels; and when a given pixel of the respective corresponding set of pixels is an inactive pixel, replace a respective predefined value for the given pixel with an estimated pixel value based on one or more active pixels in the respective corresponding set of pixels.