pstoepsi convertes EPS (and some PS) file to EPS file with Image preview.
This EPSI file is very useful to import to Tgif (with 'Ctrl-(' key).

Ghostscript has similar script (ps2epsi) but since version 7.05 it no more
creates EPSI files which are compatible with tgif.

Using is very simple:

pstoepsi input_file_name output_file_name.epsi

You will find that output_file_name.epsi in the same directory.