\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}


\newcommand{\two}{
 {\mathchoice
  {\includegraphics[height=1.6ex]{2.jpg}}
  {\includegraphics[height=1.6ex]{2.jpg}}
  {\includegraphics[height=1.2ex]{2.jpg}}
  {\includegraphics[height=0.9ex]{2.jpg}}
 }
}

\newcommand{\three}{
 {\mathchoice
  {\includegraphics[height=1.6ex]{3.jpg}}
  {\includegraphics[height=1.6ex]{3.jpg}}
  {\includegraphics[height=1.2ex]{3.jpg}}
  {\includegraphics[height=0.9ex]{3.jpg}}
 }
}
\newcommand{\gtwo}{\includegraphics[scale=0.2]{2.jpg}}
%\newcommand*{\g3}{\includegraphics[scale=0.2]{3.jpg}}
\begin{document}

\begin{equation}
\Phi(\three)-(c_1+c_2)\Phi(\two)+x_\two^\three
\end{equation}

\end{document}