Astronomical images are usually very noisy and don't shrink well with the typical lossless compression algorithms. COMPFITS is a utility program which analyses and pre-processes the images before sending them to the lossless compression program of your choice. The compression is still lossless (i.e. the reverse process gives a file exactly identical to the original) but the compression ratio achieved is usually much better. This allows fast, simple compression programs to achieve almost the same performance as time consuming, more sophisticated ones. Therefore COMPFITS is very efficient whenever computing time (for compression and/or decompression) is a critical parameter. Test charts are given to show how COMPFITS compares with other programs compressing unprocessed datas. Tests were also carried out on medical images, which are noisy too, but the results are quite different. This stresses the fact that compression of astronomical images is a specific problem. Options are available to perform lossy compression as well. COMPFITS is freely available and can be retrieved via anonymous ftp.
Astronomical Data Analysis Software and Systems III
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