Image in Equations

Question

As part of a document I'm writing, I'm trying to include an image as part of an equation, I have managed to get this to work, however the image's bottom is set to the same height as the bottom of the equation rather then the image's centre.

example code:

\begin{equation}
P_{i} = \includegraphics[scale = 0.4]{figure.pdf}
\end{equation}

I am wondering how to adjust this so that the centre line of the image is aligned with the equals sign.

Answer 1

Two solutions:

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage[export]{adjustbox}% for the second solution

\usepackage{duckuments}% for the images

\begin{document}

\begin{equation}
P_{i} =
\begin{gathered}
\includegraphics[height=3cm]{example-image-duck}
\end{gathered}
\end{equation}

\begin{equation}
P_{i} =
\includegraphics[height=3cm,valign=c]{example-image-duck}
\end{equation}

\end{document}

You can see that the centering is not “perfect” for the first case.