Lesson 7

Including Graphics and positioning

This lesson shows how you can include external graphics files into your document, how to change their appearance, and how to position or float them automatically.

To bring in graphics from outside LaTeX, use the graphicx package, which adds the command \includegraphics to LaTeX.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{graphicx}

\begin{document}
This picture
\begin{center}
  \includegraphics[height=2cm]{example-image}
\end{center}
is an imported PDF.
\end{document}

You can include EPS, PNG, JPG, and PDF files. If you have more than one version of a graphic then you can write, for instance, example-image.png. (The graphicx package will try to guess the extension if you do not give one.)

You’ll notice we’ve used a new environment here, center, to place the image horizontally centered on the page. A bit later, we’ll talk more about spacing and positioning.

Altering graphic appearance

The \includegraphics command has many options to control the size and shape of the included images and to trim down material. Some of these are used a lot, so they are worth being aware of.

The most obvious thing to set is the width or the height of an image, which are often given relative to the \textwidth or \linewidth and \textheight. The difference between \textwidth and \linewidth is subtle and often the result is the same. \textwidth is the width of the text block on the physical page, whereas \linewidth is the current width, which might locally be different (the difference is most obvious with the class option twocolumn). LaTeX will automatically scale the image so that the aspect ratio stays correct.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{graphicx}

\begin{document}
\begin{center}
  \includegraphics[height = 0.5\textheight]{example-image}
\end{center}
Some text
\begin{center}
  \includegraphics[width = 0.5\textwidth]{example-image}
\end{center}
\end{document}

You can also scale images, or rotate them by an angle. The other thing you might want to do is to clip and trim an image.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{graphicx}

\begin{document}
\begin{center}
  \includegraphics[clip, trim = 0 0 50 50]{example-image}
\end{center}
\end{document}

Making images float

Traditionally in typesetting, particularly with technical documents, graphics may move to another spot in the document. This is called a float. Images are normally included as floats so they do not leave large gaps in the page.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{lipsum}  % produce dummy text as filler

\begin{document}
\lipsum[1-4] % Just a few filler paragraphs

Test location.
\begin{figure}[ht]
  \centering
  \includegraphics[width=0.5\textwidth]{example-image-a.png}
  \caption{An example image}
\end{figure}

\lipsum[6-10] % Just a few filler paragraphs
\end{document}

Here LaTeX moves the graphic and the caption away from the Test location text to the top of the second page, because there isn’t room for it on the bottom of the first page. The ht influences where LaTeX can place the float; these two letters mean that it can go where it is in the source (next to Test location) or to the top of a page. You can use up to four position specifiers

h ‘Here’ (if possible)
t Top of the page
b Bottom of the page
p A dedicated page only for floats

Later, we will see how to cross-reference floats so you can point to them from your text.

You’ll probably spot that we’ve centered the image here using \centering rather than the center environment. Inside a float, you should use \centering if you want to horizontally center content; this avoids both the float and center environment adding extra vertical space.

Exercises

Try including an image you have created, replacing the ‘standard’ ones we have used in the demonstration.

Explore what you can do using the height, width, angle and scale keys.

Use the width key to set the size of a graphic relative to \textwidth and another graphic relative to \linewidth. Try out how they behave with or without the twocolumn option.

Use lipsum to make a reasonably long demonstration, then try out placing floats using the different position specifiers. How do different specifiers interact?