Sustainability of Digital Formats: Planning for Library of Congress Collections

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CPC, Cartesian Perceptual Compression

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name CPC (Cartesian Perceptual Compression)
Description The CPC specification defines both a datastream and an associated file format for a compressed, raster (bit-mapped) image, designed for scanned bitonal documents. The method is based on matching of symbols. Cartesian Products claims that files are typically 5 to 20 times smaller than bitonal TIFFs. The compression ratio increases for longer documents.
Production phase Potentially an initial-state or middle-state format for scanned documents; more often used as final-state format.

Local use Explanation of format description terms

LC experience or existing holdings None
LC preference For instances where bitonal images reflect content adequately, open standards, e.g., TIFF_G4, are preferable.

Sustainability factors Explanation of format description terms

Disclosure Proprietary compression scheme. Cartesian Products makes available APIs (application programming interfaces) to facilitate development of software using the scheme.
    Documentation No specification found. An overview is at

Requires plug-in or viewer for use. Various online document supply services that serve specialized audiences use CPC files for delivery, expecting recipients to download and install the plug-in or viewer. Cartesian Inc. provides a page of clients at; however, the date on this page indicates that it has not been updated since 2007.

Cartesian Inc. provides several viewers and compression tools. Viewers and decompression are free. Compression requires a purchased license after an evaluation allowance. Two APIs are available as software development kits at As of January 2014, the pages describing compression tools and viewers indicate updating in 2013 and 2014. A CPC viewer has been released for the iPad.

    Licensing and patents Patent filed in 1991 and issued in 1994 (#5,303,313). Treated in proprietary fashion.

Depends upon algorithms and tools for decompression to read; requires sophistication and access to documentation to build tools.

Two APIs are available as software development kits at

Self-documentation TBD
External dependencies None
Technical protection considerations None

Quality and functionality factors Explanation of format description terms

Still Image
Normal rendering Limited to bitonal images.
Clarity (high image resolution) Limited to bitonal images. Intended primarily for documents.
Color maintenance None. CPC is limited to bitonal images.
Support for vector graphics, including graphic effects and typography None.
Functionality beyond normal rendering None.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension cpc
Pronom PUID fmt/727
Wikidata Title ID Q5047276

Notes Explanation of format description terms


Format specifications Explanation of format description terms

Useful references


Books, articles, etc.

Last Updated: 06/17/2021