| 摘要 |
<p>Image data such as text or half-tone images is compressed and decompressed. A compressor has three phases: a bit-run length phase (32) that counts the length of each run of consecutive identical pixels; a pairs-repetition phase (36) that compresses repeated pairs of pixel run values to one copy of the repeated pair and a repeat count; and an optional dictionary-based micro-table encoder (50). The micro-table (80), which may be used in any application calling for a least recently used (LRU) mechanism, has multiple qualification layers (82, 84, and 86), with elements within a qualification layer being promoted to the next higher qualification layer upon the occurrence of a table hit for that element, and being demoted to the next lower qualification layer by being bumped by elements promoted up from below. The result is a table that is weighted both by frequency and recency of hits.</p> |
