PHOTZIP: A Lossy FITS Image Compression Algorithm That Protects User-defined Levels of Photometric Integrity | Zendy

Lior Shamir | Zendy; Robert J. Nemiroff | Zendy

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PHOTZIP: A Lossy FITS Image Compression Algorithm That Protects User-defined Levels of Photometric Integrity

Author(s) -

Lior Shamir,

Robert J. Nemiroff

Publication year - 2004

Publication title -

the astronomical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.61

H-Index - 271

eISSN - 1538-3881

pISSN - 0004-6256

DOI - 10.1086/426363

Subject(s) - lossy compression , computer science , uncompressed video , sky , smoothing , pixel , algorithm , data compression , file size , point (geometry) , image compression , compression (physics) , lossless compression , computer graphics (images) , image (mathematics) , computer vision , artificial intelligence , image processing , physics , astrophysics , mathematics , operating system , geometry , video processing , video tracking , thermodynamics

A lossy compression algorithm is presented for astronomical images thatprotects photometric integrity for detected point sources at a user-definedlevel of statistical tolerance. PHOTZIP works by modeling, smoothing, and thencompressing the astronomical background behind self-detected point sources,while completely preserving values in and around those sources. The algorithmalso guaranties a maximum absolute difference (in terms of $\sigma$) betweeneach compressed and original background pixel, allowing users to controlquality and lossiness. For present purposes, PHOTZIP has been tailored to FITSformat and is freely available over the web. PHOTOZIP has been tested over abroad range of astronomical imagery and is in routine use by the Night Sky Live(NSL) project for compression of all-sky FITS images. Compression factorsdepend on source densities, but for the canonical NSL implementation, a PHOTZIP(and subsequently GZIP or BZIP2) compressed file is typically 20% of itsuncompressed size.Comment: 10 pages, 3 figures. Accepted for publication in A

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