METHODS OF AND APPARATUS FOR ENCODING AND DECODING DATA IN DATA PROCESSING SYSTEMS

To encode and compress a data array 30, the data array 30 is first divided into a plurality of blocks 31. A quadtree representation is then generated for each block 31 by initializing each leaf node of the quadtree to the value of the data element of the block 31 of the data array 30 that the leaf node corresponds to, and initializing each non-leaf node to the minimum value of its child nodes, and then subtracting from each node except the root node the value of its parent node. A set of data indicating the differences between respective parent and child node values in the quadtree representing the block of the data array is then generated and stored, together with a set of data representing a quadtree indicating the number of bits that have been used to signal the respective difference values.