Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | CPC (Cartesian Perceptual Compression) |
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| 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. |
| LC experience or existing holdings | None |
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| LC preference | For instances where bitonal images reflect content adequately, open standards, e.g., TIFF_G4, are preferable. |
| Disclosure | Proprietary compression scheme. Cartesian Products makes available APIs (application programming interfaces) to facilitate development of software using the scheme. |
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| Documentation | No specification found. An overview is at http://www.cartesianinc.com/Tech/tech-overview.html |
| Adoption | 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. |
| Licensing and patents | Patent filed in 1991 and issued in 1994 (#5,303,313). Treated in proprietary fashion. |
| Transparency | Depends upon algorithms and tools for decompression to read; requires sophistication and access to documentation to build tools. |
| Self-documentation | TBD |
| External dependencies | None |
| Technical protection considerations | None |
| Still Image | |
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| 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 graphic effects and typography | None. |
| Functionality beyond normal rendering | None. |
| Tag | Value | Note |
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| Filename extension | cpc cpi |
| General | |
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| History |
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