Suppressing first row/column coefficients of DCT blocks for lossless JPEG code reduction

This article presents a novel method for exploiting inter/intra-block redundancies for JPEG image coding. It first expands the given image by duplicating certain rows and columns so that if f is a 8 by 8 pixel block and g and h are blocks to its immediate left and above, resp., adjacent pixels at the common boundary of f and g and at the boundary of f with h in the expanded image match. We show that the first column (row) DCT coefficients of f can be predicted without incurring any loss from the remaining DCT coefficients of f and from the DCT coefficients of g (h), assuming that the DCT is reversible. Our experiment shows that on average, we can save about 14.6% of JPEG Huffman code bits just by not coding the first row/column DCT coefficients.