AAS 205th Meeting, 9-13 January 2005
Session 153 Computation, Data Handling, Image Analysis
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[153.15] PHOTZIP: A Lossy Image Compression Algorithm That Protects Photometric Integrity

L. Shamir, R. J. Nemiroff (Michigan Tech.), Night Sky Live Collaboration

PHOTZIP is a lossy image compression algorithm that protects photometric integrity for detected point sources at a user-defined level of statistical tolerance. PHOTZIP works by modeling, smoothing, and then compressing the astronomical background behind self-detected point sources, while completely preserving values in and around those sources. The algorithm also guaranties a maximum absolute difference (in terms of sigma) between each compressed and original background pixel, allowing users to control quality and lossiness. The symmetric quantization allows for the protection of statistical properties of compressed pixel values such as the mean and median. For present purposes, PHOTZIP has been tailored to FITS format and is freely available over the web. PHOTOZIP has been tested over a broad range of astronomical imagery and is in routine use by the Night Sky Live (NSL) project for compression of all-sky FITS images. Compression factors depend on source densities, but for the canonical NSL implementation, a PHOTZIP (and subsequently GZIP or BZIP2) compressed file is typically 20% of its uncompressed size.

If you would like more information about this abstract, please follow the link to http://NightSkyLive.net. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: lshamir@mtu.edu

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.