A method of compressing data is disclosed including applying a transform
to the data to produce transformed data having a series of parts; entropy
encoding the magnitude of the transformed data of at least one of said
parts; and separately encoding the value of said transformed data.
Preferably said entropy encoding utilizes the number of non-zero
coefficients surrounding a spatial location of a corresponding
transformed data value and the entropy encoding can include encoding the
number of leading zeros in transformed data values. The method further
includes quantizing transformed portions of said data to integer values
including a sign bit and a predetermined number of coefficient bits.
Ideally, the preferred embodiment includes wavelet transforming the data
with each of the sub-band components of the wavelet transform being
separately entropy encoded. The present invention is ideally suited to
the compression of image data.