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

• US 20010031092A1
• Filed: 12/04/2000
• Published: 10/18/2001
• Est. Priority Date: 05/01/2000
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Kang, Sang-Chul, Eldridge, George L., Nelson, William E., Crean, Peter A., Rumph, David E., Zeck, Norman W.
• Granted Patent: US 6,731,814 B2
• Time in Patent Office: Days
• US Class Current: 382/239
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00

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.

Claims

1. A method of compressing a received document, comprising:

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.

2. A method as described in

claim 1

, wherein scanned data is further segmented into plural scanned data types, and each data type is compressed in said compressing data step with a compression method optimized for said scanned image data type.

3. A method as described in

claim 1

, wherein for received compressed data,

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.

4. A method of compressing received documents including:

receiving documents containing unknown combinations of a plural data types, including combinations of scanned data, computer rendered data, compressed data and/or rendering tags;

classifying each data type present in the received document;

determining optimum compression of each data type present, which may include a non-compressing pass thought of compressed data;

from said optimum compression determination, generating a decompression instruction stream, useful in decompression of the document, and which includes decompression instructions and document data.

5. A data structure, for describing a compressed document including unknown combinations of plural data types, including combinations of scanned data, computer rendered data, compressed data and/or rendering tags, comprising:

segregation of data in accordance with compression methods thereof;

segregation of data into independent block and strip document portions, whereby each block document portion and each strip document portion may be compressed or decompressed without reference to any other block and strip, respectively.