Tiled Image Compression Convention
A convention for compressing FITS images and storing the compressed
byte stream in a variable-length array column in a
FITS binary table. Optionally, the image may be divided
into rectangular tiles, and each tile is compressed separately. Any
number of different compression algorithms can be supported. Current
implementations support GZIP, RICE, H-Compress, and the IRAF pixel list compression
Version 2.0 in November-2006 by W. Pence, NASA/GSFC (on behalf of the authors).
Updated to version 2.1 in August 2009.
Registered: March 2007
Date and Place of First Usage:
circa 2001: support for this image compression convention was
implementd in the CFITSIO library that is maintained by the HEASARC.
Soon after, support for pixel lists in this compressed format
was added to IRAF.
Extent of Usage:
This convention has been moderately used, e.g., by the
Canadian Astronomy Data Center (CADC) and by the Optical Gravitational Lensing
Experiment (OGLE). There are plans to use this convention to compress
the many terabytes of imaging data in the next generation of the NOAO Science Archive.
Latest 2.2 version (May 2011):
Modified Section 3 to document the optional "GZIP_COMPRESSED_DATA" column, which provides an alternative
compression method for floating-point image tiles that cannot be compressed with the usually quantization
Previous 2.1 version (August 2009):
Modified Section 4 and Appendix A to describe a new "subtractive dithering" technique which preserves more information when
quantizing floating-point FITS images.
Previous 2.0 version (November 2006):
Sample FITS Files (all files contain the same image of Messier 13)
Sample Header Listing:
rice compressed image header listing
Last revised: Monday, 09-May-2011 15:37:33 EDT
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Responsible NASA representative: Dr. William D. Pence
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