Set standard default scaling of \includegraphics

Question

I am using Sphinx and the plantuml package to include UML diagrams.

The plantuml package for Sphinx generates the following LaTeX code:

\includegraphics{%s}

Anyways - the diagrams are to big, so what I want is

\includegraphics[scale=0.75]{%s}

Can I - without patching the plantum package - set a default scale for \includegraphics in my LaTeX preamble?

Answer 1

There are two ways.

First way: set a default value for some keys.

\usepackage{graphicx}
\setkeys{Gin}{width=.75\csname Gin@nat@width\endcsname,keepaspectratio}

(the natural width is stored in \Gin@nat@width)

Second way: add scale=0.75 to the passed options.

\usepackage{graphicx}
\let\ORIincludegraphics\includegraphics
\renewcommand{\includegraphics}[2][]{\ORIincludegraphics[scale=0.75,#1]{#2}}

Answer 2

There is a way to define standard options for \includegraphics, but unfortunately, it doesn't seem to work for scale. It works for width though, which might be an option, too? See section 4.6 of grfguide: Global setting of keys.

\documentclass{article}

\usepackage{graphicx}
    \setkeys{Gin}{width=.75\textwidth, height=1cm}
    % in your case, you'd obviously only specify the width
    % I just used height as well for demonstration purposes.

\usepackage{mwe}% just for the example images

\begin{document}\centering

\includegraphics{example-image-16x10}

\includegraphics{example-image-1x1}

\includegraphics{example-image-a4-landscape}

\includegraphics{example-grid-100x100pt}

\end{document}

Note that the images originally all have different aspect ratios.