Patent ID: RE43649

Claim:
A method of image compression comprising the steps of: (a) dividing an image to be compressed into a plurality of image blocks; (b) carrying out a two-dimensional block transform on each block to produce a corresponding plurality of coefficient blocks; (c) bitwise digitizing the coefficients within each coefficient block to define a plurality of bit planes for each coefficient block; (d) defining a group of one or more consecutive bit planes starting with the most significant bit plane; (e) selectively flagging those , by a coder device, coefficients which first become significant within the a group of one or more consecutive bit planes of corresponding coefficient blocks of image blocks resulting from a block transform, starting with the most significant bit plane ; and (f) transmitting , by the coder device, information representative of the positions of the said flagged coefficients and transmitting the bits within the a group of the said flagged coefficients ; and, (g) repeating steps (d) to (f) one or more times, with each new group starting with the most significant bit plane not previously dealt with and, at each repeated pass, also transmitting the bits within the current group of those coefficients which were previously flagged on an earlier pass .