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FITS Image compression, is it portable?
Hi,
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. Any comments/info? -- Carsten A. Arnholm http://arnholm.org/ N59.776 E10.457 |
#2
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FITS Image compression, is it portable?
On Wed, 31 May 2006 16:05:48 +0200, "Carsten A. Arnholm"
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 |
#3
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FITS Image compression, is it portable?
Carsten A. Arnholm wrote:
Hi, 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. Any comments/info? I dont know if the softwares you mention implement compression but my impression is that compression is not widely used because developers do not implement compression ; and the main reason while they do not implement compression is because it is not widely used. I am also working on a small software manipulating fits file, so let's make a collegial decision (no doubt that our 2 softwares together will promote this decision to a de facto standard and decide we both implement compression in our software. At least, if the world continues to ignore our contributions, our softwares will be compatible with each other. best regards -- -- francois meyer http://dulle.free.fr/alidade/galerie.php?maxim=12 |
#4
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FITS Image compression, is it portable?
Hi,
Chris L Peterson wrote: I've found that support for compressed files is inconsistent. Some apps use their own compression, which isn't compatible with the FITS standard. Yes, it is not very nice behaviour ..... it makes standard compliant programs fail. I assume you are using the CFITSIO library, Yes. 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. That is the whole issue, really. My question was about portability, i.e. between applications. 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. This is actually a decent solution, as it is - very simple to implement - safe (you are sure to not lose the data) - consistent with the way people use compression elsewhere - compatible with CFITSIO (I tried it and it works!) - if people are using an application that doesn't support FITS compression they can unzip using winzip and still get it to work So I think you have a good point, thanks! Clear skies Carsten A. Arnholm http://arnholm.org/ N59.776 E10.457 |
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