Method of further compressing JPEG image

摘要

Recovered 8x8 DCT coefficient arrays of all block of a JPEG image is formed by reversely decompressing the JPEG image till the procedure of dequantization. A method of redundancy removal of inter-block same subband AC coefficient and intra-block adjacent subband DCT coefficients is applied by re-ordering the coefficients by magnitude of the neighboring subband or a weighted sum of those. The differential values of both inter-block and intra-block DCT coefficients are calculated and coded by an entropy coder to further reduce the data rate. A short code is assigned to represent the "end of non-zero" of each re-ordered subband AC coefficients.