CFITSIO is the closest you can get to the pixels in a FITS image while remaining faithful to the FITS standard. It is written by William Pence, the principal author of the FITS standard31, and is regularly updated. Setting the definitions for all other software packages using FITS images.
Some GNU/Linux distributions have CFITSIO in their package managers, if it is available and updated, you can use it. One problem that might occur is that CFITSIO might not be configured with the --enable-reentrant option by the distribution. This option allows CFITSIO to open a file in multiple threads, it can thus provide great speed improvements. If CFITSIO was not configured with this option, any program which needs this capability will warn you and abort when you ask for multiple threads (see Multi-threaded operations).
To install CFITSIO from source, we strongly recommend that you have a look
through Chapter 2 (Creating the CFITSIO library) of the CFITSIO manual and
understand the options you can pass to
$ ./configure (they aren’t
too much). This is a very basic package for most astronomical software and
it is best that you configure it nicely with your system. Once you download
the source and unpack it, the following configure script should be enough
for most purposes. Don’t forget to read chapter two of the manual though,
for example the second option is only for 64bit systems. The manual also
explains how to check if it has been installed correctly.
CFITSIO comes with two executables called fpack and funpack. From their
manual: they “are standalone programs for compressing and uncompressing
images and tables that are stored in the FITS (Flexible Image Transport
System) data format. They are analogous to the gzip and gunzip compression
programs except that they are optimized for the types of astronomical
images that are often stored in FITS format”. The commands below will
compile and install them on your system along with CFITSIO. They are not
essential for Gnuastro, since they are just wrappers for functions within
CFITSIO, but they can come in handy. The
make utils command is
only available for versions above 3.39, it will build these executables
along with several other test executables which are deleted before the
installation (otherwise they will also be installed).
The CFITSIO installation from source process is given below. Let’s assume you have downloaded cfitsio_latest.tar.gz and are in the same directory:
$ tar xf cfitsio_latest.tar.gz $ cd cfitsio $ ./configure --prefix=/usr/local --enable-sse2 --enable-reentrant $ make $ make utils $ ./testprog > testprog.lis $ diff testprog.lis testprog.out # Should have no output $ cmp testprog.fit testprog.std # Should have no output $ rm cookbook fitscopy imcopy smem speed testprog $ sudo make install
Pence, W.D. et al. Definition of the Flexible Image Transport System (FITS), version 3.0. (2010) Astronomy and Astrophysics, Volume 524, id.A42, 40 pp.