How to include eps files in Plain TeX?

Question

The title stands for itself.

If it is not possible, how does LaTeX import an EPS file using \includegraphics?

Answer 1

There is a package epsf.tex by Tom Rokicki. Try

\input epsf

\epsfbox{myfile.eps}

\bye

Reading the file epsf.tex (in my system it is /usr/local/texlive/2012/texmf-dist/tex/generic/epsf/epsf.tex) will give you an insight into the way TeX works with postscript graphics.

Answer 2

The LaTeX package graphicx also can be used in plain TeX with the help of miniltx.tex. For driver dvips.def there is already a TeX file that can be loaded:

\input graphicx.tex
\includegraphics{myimage.eps}

The file graphicx.tex contains:

\input miniltx

\def\Gin@driver{dvips.def}
\input graphicx.sty

\resetatcatcode

Usually the TeX distribution has an intelligent graphics.cfg that can detect some of the drivers (pdfTeX/LuaTeX, XeTeX) and sets a default driver (usually dvips) otherwise, then

\input miniltx.tex
\input graphicx.sty
\resetatcatcode

would be enough and the the driver definition is only needed, if other DVI drivers are used. (Also other LaTeX packages can be used in plain TeX, e.g. ifpdf, ifxetex, ...).