Method for image encoding

Abstract

A method for encoding data defining an image is disclosed. The method comprises segmenting the image into image blocks having a uniform size; and applying a frequency-based transform to each resulting in transformed image data in which the image data is represented as coefficients defining a linear combination of predetermined basis functions having different spatial frequencies, with each block of transformed image data having one coefficient for a zero frequency basis function, and a plurality of coefficients for higher frequency basis functions, which are grouped into one or more sub-bands. The blocks of transformed image data are grouped into slices, and the coefficients are converted into binary code using an allocation method to allocate bits associated with coefficients in each sub-band in a slice amongst-substantially same length bins. Bits associated with each sub-band in each slice are assigned to a bin and transferred, if needed, to achieve the substantially same length.