A method and encoding unit for encoding a block of pixels into a compressed data structure determines a set of Haar coefficients for a 2×2 quad of pixels of the block of pixels, which set includes a plurality of differential coefficients and an average coefficient. A first portion of the compressed data structure is determined using the differential coefficients and includes a first set of bits which indicates an order of the magnitudes of the differential coefficients, and a second set of bits which indicates a sign and an exponent for each of one or more of the differential coefficients which are non-zero. A second portion of the compressed data structure is determined using the average coefficient determined for the 2×2 quad of pixels. The compressed data structure is stored.