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Cartesian Perceptual Image Compression

The Cartesian Perceptual Compression (CPC) is a novel image compression method developed by Cartesian Products, Inc., which was specifically designed for 1-bit/pixel document image storage and transmission systems. In many instances this proprietary compression scheme has shown to reduce the size of scanned image files by almost an order of magnitude (typical compression ratios range from 5 to 10 over TIFF G4 encoding).

The Astrophysics Data System is considering making its collection of full-text articles available in this format, and would like to receive some feedback from potential users who may benefit from it. A number of viewers capable of displaying and printing images in this format are currently available from Cartesian Products, Inc. Please notice that a only limited number of options for viewers are currently available, and that the viewer for Windows platforms is currently free only on a trial basis.

MS Windows viewer

If you're using a WWW browser under MS Windows95/98/NT, then you should download the 90-trial version of CPC View, a plugin for Netscape and Internet Explorer versions 3.0 and above. Installation instructions and documentation are provided on the download pages.

UNIX and Macintosh viewer

A free CPC viewer plugin called CoPyCat exists for the Macintosh and a few UNIX flavors (HP-UX, Solaris, SGI IRIX). CoPyCat which work as an add-on to Adobe's Acrobat Reader, which is also available free of charge. Unfortunately, at the moment no documentation is available on the installation and use of CoPyCat from Cartesian Products, Inc., but here is a brief overview of the installation steps under unix for setting up CoPyCat as a netscape plugin:

  1. Make sure that Acrobat 3.0 is installed on your system and available in your path (type which acroread to verify availability)
  2. Identify the directory under the Acrobat Reader installation tree which holds the netscape plugin (this is a file named For instance, under Solaris, this directory is typically named something like: /dir/.../Acrobat3/Browsers/sparcsolaris.
  3. Create a directory under your home directory which is going to hold the CoPyCat plugin:
    mkdir $HOME/netscape $HOME/netscape/plugins
  4. Point your web browser to the Cartesian Download Library page:, identify the version of CoPyCat appropriate for your platform, click on the "Download" link, and save the contents to the plugins subdirectory created in the previous step.
  5. Make the downloaded file executable:
    chmod +x $HOME/netscape/plugins/*
  6. Tell netscape to look for the Acrobat Reader and CoPyCat directories for plugins. This can be accomplished by appending the new directory name to the list of directories listed in the environment variable NPX_PLUGIN_PATH, e.g.:
    setenv NPX_PLUGIN_PATH /opt/local/lib/netscape/plugins:/opt/local/lib/Acrobat3/Browsers/sparcsolaris:$HOME/netscape/plugins
  7. Start netscape and verify that both the acroread and CoPyCat plugins are available by clicking on "Help" -> "About Plugins." An entry listing and CoPyCat as the plugins for the Mime Types application/pdf and image/cpi, respectively, should be displayed.
Note: you may find it convenient to create a wrapper script that sets the environment properly before lauching netscape. For instance, this is what I use:
#! /bin/sh


exec netscape4.05 "$@"

Sample Documents in CPC Format

We have created selected number of documents from the ADS article archives in CPC format as well as Postscript level 2 and PDF. All files listed are created from high-resolution (600dpi) scanned images of individual articles.