Patent ID: 6978048

Claim:
A method of encoding a digital image comprising a plurality of pixels, the image being able to be transformed by a discrete wavelet transform (DWT) to a predetermined level of decomposition, and capable of being encoded on a block by block basis, each block having a specified block size in number of coefficients, in a first dimension and a second dimension, the method comprising the steps of: a) dividing the image into a plurality of tiles, each tile having firstly, substantially a minimum number of pixels required to produce the number of coefficients in the first dimension of the block at the predetermined level of DWT decomposition, wherein the predetermined level of DWT decomposition is greater than one, and secondly, less than a minimum number of pixels required to produce the number of coefficients in the second dimension of the block at the predetermined level of DWT decomposition; b) selecting a current tile; c) decomposing the current tile, using the DWT, to one level of decomposition to form a plurality of subbands including a LL, LH, HL and HH subband; d) accumulating coefficients in each subband of the LH, HL and HH subbands to form blocks of the specified block size, and encoding each block to a bit stream; e) accumulating LL subband coefficients and repeating steps b) to e) until a predetermined number of coefficients, dependent on the specified block size, of the LL subband have been accumulated; f) assigning as a current tile the predetermined number of accumulated LL sub-band coefficients; g) repeating steps c) to f) until the predetermined level of DWT decomposition is reached; and h) encoding the LL subband into the bit stream.