fv [L1 ] is an editor for image files in FITS format.
fv 4.4 uses Tcl/Tk, Tix, itcl/itk/iwidgets, pgplot, fitsTcl, and other dependencies.
fv is supplied as a standalone binary; however if the correct components are built and installed, it can be run as a Tcl/Tk script in an ordinary Wish interpreter. These components include the standard extensions Itcl, Itk, Iwidgets, Tix, tclreadline, pgplot, plt and pow, and the specialist extensions tclxpa and fitsTcl that are provided with fv itself.
ds9 can be used as the display for fv: start ds9 and select it as the "Display Device" from fv's main menu.