Re: FITS Image compression, is it portable?



On Wed, 31 May 2006 16:05:48 +0200, "Carsten A. Arnholm"
<arnholm@xxxxxxxxxx> wrote:

I am writing some software to read, process and write FITS files. I was
wondering about the options for FITS image compression, i.e.
<http://heasarc.gsfc.nasa.gov/docs/software/fitsio/c/c_user/node40.html>

Does anyone know if other popular programs implement this? I.e. MaximDL,
AstroArt, Photoshop (via FITS Liberator) and the like?

If no-one implements such compression, then it makes no sense for me to do
it either, because the FITS files must be portable between applications.

I've found that support for compressed files is inconsistent. Some apps
use their own compression, which isn't compatible with the FITS
standard. I assume you are using the CFITSIO library, and
comression/decompression functions are included, so there is little
reason not to include support- just be aware that apps using their own
FITS engines will likely not be compatible.

In general, there is very little reason to use FITS compression. If you
want to compress image files, IMO you are better of doing it externally
by simply zipping them into an archive using a third party app, or the
folder compression built into most operating systems.

A single image file compressed as .ZIP, .Z, or .GZ will be expanded and
opened automatically by CFITSIO.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.