GAMGI uses the file extension to automatically determine the
file format. To export a standard .tiff file of the whole
graphic area of a top window, just give the filename the
extension .tiff or .tif.  The command line application
pnmtotiff, widely available and usually installed by default in
most Linux distributions, must be installed, otherwise GAMGI
will be unable to export a .tiff file.  This a large-size, high-
quality, widespread format, which is particularly suitable to
distribute among systems that might not support .png files very
well.