1. A method of wavelet filtering a digital image, the digital image comprising a plurality of pixels arranged in one or more bands of pixels, the method performing the following steps for each one of said one or more bands of said pixels: retrieving a plurality of previous partial results from a first or second storage; inputting a current group of adjacent said pixels; computing coefficients utilising said current group of adjacent pixels and said plurality of previous partial results; outputting said coefficients; and storing a plurality of current partial results in said first storage if said current group is not the last group in the band, in said second storage if said group is the last group in the band.