| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for compressing a raster image at a high compression rate. SOLUTION: First re-ordering (602) data compresses a raster image at a high compression rate. Then indexing the data subject to re-ordering encodes all optional predicted runs and literal runs (Figure 5). Each part of a current line of the raster image is compared with that of a preceding line. When the result of comparison indicates coincidence, it means that the current line parts are predicted runs (Figure 5) and they are indexed accordingly (603). When the result of comparison indicates dissidence, it means that the current line parts are literal runs (Figure 5) and they are indexed accordingly (603). Employing an reversible compression method such as the Huffman coding compresses an index string (Figure 4) next (604). A Huffman table is made adaptive when a compressor compresses the index string (705, 706). The compressor informs a decoder about it when the adaptive table is to be used.
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