How to include a jpg file on your latex file:

\documentclass[12pt]{article}
\usepackage{graphicx}
\DeclareGraphicsRule{.JPG}{eps}{*}{`jpeg2ps #1}
\newcommand{\mypic}[2]{\begin{figure}\begin{center}\includegraphics [width=#1\textwidth , bb= 20 20 575 575]{#2}\end{center}\end{figure}}

\begin{document}
\mypic{.5}{mountain.jpg}
\end{document}

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Here is how you can include eps files on your latex file (you have more control).

\documentclass[12pt]{article}
\usepackage{epsfig}
\newcommand{\mypicture}[2]{\epsfig{figure=#2.eps,width=#1cm}}% change the location of your ps files here.
\begin{document}

Here is another one

\mypicture{7}{mountain}

it is nice.
\end{document}