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Cartesian Perceptual Compression (CPC) is a novel patented image
compression method specifically designed for document image storage
and transmission systems.
Why compression is important
Increasingly, businesses are storing scanned images of documents on
computers and transmitting them over the Internet, over local-area
networks, and over the phone lines. Such scanned documents require
huge amounts of storage space and transmission time, which directly
affects the cost of the storage or transmission. Therefore, document
storage and transmission systems and fax machines use some kind of
image compression technology -- typically the so-called CCITT Group 3
and Group 4 methods -- to compress the data to a fraction of its
original size. In this way, pages can be stored in less space and
transmitted in less time. Of course, still better compression
technology would yield commensurate benefits in decreased storage and
transmission requirements and associated cost savings.
The Cartesian advantage
The Cartesian compression method allows for the storage of documents in a fraction of the space that would be required when using today's best alternative technology. For instance, randomly selected documents have been compressed 20 to 30 times smaller than the industry-standard CCITT Group 4 compression method. Results across a broad spectrum of documents indicate that improvement of 10 to 1 over the Group 4 method is quite common. Based on these findings, whereas a 1 megabyte floppy disk can hold only a single uncompressed page image at 300 DPI, or perhaps images of a short report if compressed with Group 4, our compression method frequently allows page images of an entire book to be stored on a single floppy disk. The advantage for optical disks is commensurate.
For example, a sample six-page legal document can be compressed by Cartesian's method over 600 to 1, which is almost 50 times better than Group 3 and over 20 times better than Group 4, as shown in this table:
| Compression method | Size (bytes/page) | Compression ratio | Cartesian advantage |
|---|---|---|---|
| Uncompressed | 1056000 | -- | 610.9 : 1 |
| Group 3 1D | 84099 | 12.6 : 1 | 48.7 : 1 |
| Group 3 2D | 63419 | 16.7 : 1 | 36.7 : 1 |
| Group 4 | 37326 | 28.3 : 1 | 21.6 : 1 |
| Cartesian | 1728 | 610.9 : 1 | -- |
Other examples and further technical details are available in a technical overview of the compression
technology.
The CPC Software Library
Our current version of Cartesian Perceptual Compression, CPC V3.3, is
designed to run interoperably on multiple computer architectures
including SPARC, MIPS, Motorola 680x0, and Intel x86 running under
UNIX and Windows.
The software library has a simple application programmers' interface, and the software development kit comes with a complete sample compression/decompression application.
The CPC Software Library has been used to build CPC View and
CPC Tool, viewer and compressor software for documents stored
in CPC, TIFF, and PBM image formats. These software tools are freely
available from Cartesian Products. You can use
them today to gain the advantage of CPC compression.
Who is Cartesian Products?
Cartesian Products, Inc. is a high-technology research and development company based in Cambridge, Massachusetts. The company was founded in September 1991 to provide advanced software technology to improve worldwide communication and information access. Further information on the management of CPI is available.
Cartesian Compression, the company's first invention, is an efficient method for compressing document images. The invention regularly compresses document images an order of magnitude better than industry-standard compression methods. Such dramatic compression opens up whole new application areas for document images by allowing storage of full images in about the space required previously for the textual information alone.
The invention has especially far-reaching implications for the fax and document image management industries. For the fax industry, the compression method can cut fax transmission time, thereby significantly reducing telephone charges while improving resolution. For the document image management industry, the method can cut storage requirements dramatically, thereby allowing for lower hardware costs, faster image retrieval, and better performance.
Cartesian Products has been granted a United States patent on its technology and has applied for patent protection abroad.
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