Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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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 https://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. Cartesian Inc. provides a page of clients at https://www.cartesianinc.com/General/clients.html; 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 https://www.cartesianinc.com/Tech/API/. 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. |
| Transparency |
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 https://www.cartesianinc.com/Tech/API/. |
| 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 vector graphics, including graphic effects and typography | None. |
| Functionality beyond normal rendering | None. |
| Tag | Value | Note |
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| Filename extension | cpc cpi |
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| Pronom PUID | fmt/727 |
See https://www.nationalarchives.gov.uk/PRONOM/fmt/727. |
| Wikidata Title ID | Q5047276 |
See https://www.wikidata.org/wiki/Q5047276. |
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| History |
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