I don't think I'm able to change the open/closed status and the progress of a ticket once it's closed

I don't think this task is complete: gnuastro programs still don't compress the output file when it has ".fits.fz" extension.

I explained the installation of fpack and funpack in the manual. However, when I try opening the attached file (in the previous comment) in Gnuastro (for example converting it to JPEG), I get the following error:

astconvertt convolve_spatial_warped.fits.fz --output=jpg

astconvertt: Currently only a 2 dimensional image array is supported. Your array is 0 dimension(s). This might Be due to the fact that the data in images with multiple extensions are sometimes put on the second extension. If this is the case, try changing the hdu (maybe to --hdu=1).

It appears that CFITSIO will not automatically unpack the compressed file. Having a look at the "Image Compression" section of the CFITSIO manual, it is indeed necessary to do some operations before giving the file names to CFITSIO. We should add those operations when the input has a fits.fz suffix so something like the simple command above can work.

Ok, when I get the chance I will have a look at this issue, thanks for all the basic information ;-).

In the mean time, is it possible for you to introduce a sample .fits.fz file for future reference? If any public survey hosts public data, it would be great if you can put a link to its files in this task. Alternatively, if you have publicly released data in this format, you could attach a (small) crop of such a file to this task.

Ofcourse, we are working on outputs now, so as input, I can use a normal FITS image, but I would just like to to have a reference to the standard ways this format is used for the future, at least in my field (deep galaxy imaging surveys), none of the surveys I am familiar with use this format (or maybe they have but I haven't noticed!), so such a reference would be very useful.

For tasks like ImageCrop which fills parts of the output image that overlap with the inputs (in WCS mode), I think it might be easier to first let it save in FITS, then after the job is finished, read in the FITS image and save it as the output fits.fz format and then delete the FITS file. I am guessing that the compression and decompression on a tiled binary table for each input image can (possibly) make it much slower when multiple images are concerned.

I was testing "astimgcrop" and it can't write compressed files because it uses "fits_write_null_img" to write the fits file and this function ("ffpprn" in CFITSIO code) doesn't support writing to compressed files.  Instead, "fits_write_img" does.  Mohammad, could you please give it a look when you have time?  You're more familiar than me with CFITSIO functions and internals of Gnuastro.  No rush ;-)

The syntax to select a compressed output file is described in section 5.6 of CFITSIO manual, the simplest case is

$execname [OPTIONS...] $input --output="output.fits[compress]"

Quotes are required in order to prevent the shell from interpreting the brackets as a regular expression.

Please also note that TLONG and TULONG datatypes are not supported anyway.  So, for example, "astmknoise" uses "fits_write_null_img" to write the files but the datatype is TLONG.  Instead, "astimgwarp" with "--doubletype" option works flawless.

It turned out that there wasn't much to do: "nameisfits" and "nameisfitssuffix" didn't accept a file with "fits.fz" extension, once you add that to the list of acceptable extensions Gnuastro is able to read fpacked fits files.

The problem now is that Gnuastro doesn't compress output files even if they have ".fits.fz" extensions, contrary to what happens with ".fits.gz", but I think this should be addressed in another task.

Gnuastro is able to read FITS compressed with gzip, but not those compressed with fpack.  CFITSIO should give the tools to do that anyway.