US Patent 9503123 Random access to compressed data using bitwise indices

Methods and apparatus are provided for random access to compressed data using bitwise indices, enabling interaction with compressed data as if interaction were with an uncompressed version thereof. A compressed file is decompressed using an index table comprising a bitwise mapping between individual bits in the compressed file and corresponding portions of an uncompressed version of the compressed file; and decompressing at least a portion of the compressed file using the index table. Different data types within a file are optionally managed by separate index tables. A block-based file system can process index tables to provide transparent access to the compressed file. The index tables support dynamic index granularities, without decompressing the compressed file and recompressing it. The decompressed portion of the compressed file is optionally stored in a cache, possibly with neighbor portions pre-fetched using the index tables. Multi-resolution compression and quality-based decompression are also provided without space overhead.