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FITS Image compression, is it portable?



 
 
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  #1  
Old May 31st 06, 03:05 PM posted to sci.astro.amateur
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Default 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  
Old May 31st 06, 03:40 PM posted to sci.astro.amateur
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Default 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  
Old May 31st 06, 03:46 PM posted to sci.astro.amateur
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Default 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  
Old May 31st 06, 09:52 PM posted to sci.astro.amateur
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Default 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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