The present invention relates to an improved method and apparatus for image compression and particularly to an improved block coding apparatus and method for compression for use with the JPEG2000 standard, although not limited to this. Methods for coding and decoding blocks and subbands samples derived from still images video frames or related media, involving three bit-streams and the partitioning of samples from the blocking to define groups, is provided. A first bit-stream encodes the significance of whole groups. A second bit-stream encodes the significance of individual samples within each group. The second bit-stream also encodes an unsigned residual value for each significant group. A third bit stream provides a sign bit and any additional magnitude bits required to represent the significant sample values. Exponent predictors are computal using both exponent bounds and the additional magnitude bits associated with previous samples in the block.