System requirements: Tcl/Tk (>= 8.6). To read and write other formats
than PPM/PGM, PNG and GIF it is required the 'tkImg' for
'Tcl/Tk' (https://sourceforge.net/projects/tkimg/), or the
debian 'libtk-img' package (Ubuntu) or the RPM 'tkimg' package
(Fedora or openSUSE).