FITS compression

[William Pence]

A Proposal for Representing Compressed Images in FITS Format
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A small group of us have been experimenting with ways to represent compressed
images in FITS format and have drafted a proposal that we would like to submit
for comments or suggestions from other FITS users.  The current draft proposal
is available in html format at:

http://legacy.gsfc.nasa.gov/docs/heasarc/fits/compress/compress_image.html

or in postscript format at

http://legacy.gsfc.nasa.gov/docs/heasarc/fits/compress/compress_image.ps

In brief, our proposed technique is to first divide the n-dimensional image into
a rectangular grid of one or more subimages or 'tiles', then compress each tile
individually and store the resulting byte stream in a row of a variable-length
column in a binary table.  Any number of different compression algorithms may be
supported by this convention and we specifically describe a few possible
algorithms in the appendixes to the proposal.  The appendixes are currently
incomplete, but we eventually intend to provide a complete description of each
supported compression algorithm.

We are currently developing prototype implementations of this proposal.  In
particular, I will be giving a presentation at next month's ADASS meeting that
gives a progress report on supporting this convention from within the CFITSIO
library.  

Bill Pence, NASA/GSFC, on behalf of
Richard White, STScI
Perry Greenfield, STScI
Doug Tody, NOAO