Method for compressing digital documents with control of image quality and compression rate

Abstract

A method and apparatus for compressing and decompressing electronic documents, with maximum intradocument independence, and maximum flexibility in optimization of compression modes. The method includes receiving documents containing unknown combinations of a plural data types, including combinations of scanned data, computer rendered data, compressed data and/or rendering tags; dividing the received image into strips of blocks determining from the image itself, which data types are present in each block; compressing data of each data type present in each block with a compression method optimized for its data type. Scanned data may be further segmented into plural scanned data types, where each data type is compressed in said compressing data step with a compression method optimized for said scanned image data type. If the received data type is compressed data, the process may include the additional functions of determining a compression ratio thereof, and accepting the compressed data for use as, or decompressing and recompressing the data, based on acceptability of said compression ration determination. An instruction set is generated that allows detailed decompression instruction data and image data to be combined with transmitted compressed data. A data structure is shown, which segregates data types and instruction data, and allows for block to block and strip to strip processing independence.

Dependencies are inferred from the claim text.