METHODS AND APPARATUS FOR IMAGE-DATA DECOMPRESSION

摘要

A system is described for processing a sequence of groups of compressed quantized transform coefficients representing a two-dimensional image. The system comprises special-pattern testing means for determining for each group of compressed quantized transform coefficients in turn whether the group corresponds to one of a predetermined plurality of special patterns of zero and nonzero quantized transform coefficients. Furthermore, the system includes a plurality of special-pattern inverse transform means, each special-pattern inverse-transform means being associated with one of the special patterns of zero and nonzero quantized transform coefficients for performing an inverse scaled two-dimensional discrete-cosine-transform process on groups of transform coefficients determined by the special-pattern testing means to correspond to the associated special pattern. Finally, full inverse-transform means are provided for performing an inverse scaled two-dimensional discrete-cosine-transform process on groups of transform coefficients determined by the special-pattern testing means not to correspond to any of the predetermined plurality of special patterns of zero and nonzero quantized transform coefficients. <IMAGE> <IMAGE>