[gnuastro-devel] [task #14191] Enable FITS input and output using Lzip

[Mohammad Akhlaghi]

URL:
  <http://savannah.gnu.org/task/?14191>

                 Summary: Enable FITS input and output using Lzip
                 Project: GNU Astronomy Utilities
            Submitted by: makhlaghi
            Submitted on: Wed 26 Oct 2016 08:50:50 PM JST
         Should Start On: Wed 26 Oct 2016 12:00:00 AM JST
   Should be Finished on: Wed 26 Oct 2016 12:00:00 AM JST
                Category: All Gnuastro
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: Postponed
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

    _______________________________________________________

Details:

Lzip <http://www.nongnu.org/lzip/> is a compression format that has both a
high compression ratio and archival capabilities (can detect corruption in the
data with high completeness). 

CFITSIO does already allow .fz <https://heasarc.gsfc.nasa.gov/fitsio/fpack/>
(only for FITS images) and .gz <https://en.wikipedia.org/wiki/Gzip>
internally. So inputs and outputs can easily be done with these two
compresssions in Gnuastro. 

As a small test on this XDF survey image
<http://archive.stsci.edu/pub/hlsp/xdf/hlsp_xdf_hst_acswfc-60mas_hudf_f850lp_v1_sci.fits>
(originally 106Mb) and using the default output of all the compressors, Gzip's
output is 44Mb, Lzip is 41Mb and the `.fz' file is 7Mb. 

However, note that the `.fz' file is lossy, so the original values are
slightly changed, you can tell with the 0 valued pixels in the original image
that are no longer 0 in the `.fz' output.  

For Lzip, we will have to use the Lzip library to internally
compress/decompress the files in input and output. 

The only problem is Lzip inputs and outputs is that SAO ds9
<http://ds9.si.edu/site/Home.html> (and probably other FITS viewers) don't not
currently open `.fits.lz' files directly (for easy viewing), while it opens
`.fits.gz' and `.fits.fz' easily. We might be able to get in touch with those
viewers' developers and ask them to integrate Lzip.




    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/task/?14191>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/