# \includegraphics optional argument not resolved if macro

\documentclass[a4paper,10pt,twoside]{book}
\usepackage[demo]{graphicx}

\begin{document}

\newcommand{\scalefactor}{scale = 0.25}

\begin{figure}[!ht]
\centering
%Next line does not work
\includegraphics[\scalefactor]{image}
% The following line works
%\includegraphics[scale = 0.25]{image}
\end{figure}

\end{document}


Output:

! Package keyval Error: scale = 0.25 undefined.


I need to scale a number of images by the same factor, hence the command.

1. How to solve this and more importantly
2. Why is this only specific to \includegraphics
-
You can see why it's a problem if you use \expandafter\includegraphics\expandafter[\scalefactor]{image} which is longer than the intented shortcut. –  percusse Feb 8 at 12:31
It's not specific only of \includegraphics but of most (if not all) arguments that consist of key=value options. –  egreg Feb 8 at 12:35
@percuße I don't use this directly, it is nested in another macro, will using \expandafter hurt the general case? If not clear please let me know I will edit the question –  aiao Feb 8 at 12:47
The problem here is that the key=value algorithm has to see the = to split both parts. If it is included in a macro it can see it and therefore the whole macro is incorrectly taken as one value-less key, which is of course not defined. –  Martin Scharrer Jun 25 at 10:30

Try this way:

\newcommand{\scalefactor}{.25}
\includegraphics[scale=\scalefactor]{image}

-
ooh I was just saying that your posted 10 seconds before my edit went on so + 1 :-) –  David Carlisle Feb 8 at 12:52

If you use

\setkeys{Gin}{scale=0.25}


that key value will be in force by default until you change it, so there is no need to use a LaTeX command macro syntax here.

If your issue is that you want to set the value somewhere else you can go

\newcommand{\scalefactor}{0.25}
...
\includegraphics[scale = \scalefactor]{image}

-
As far as I understand this is global scaling factor. If this is the case, then this wont work for me because I scale only specific images –  aiao Feb 8 at 12:40
well it's local to the current environment or group, or you can set it back to 1 explicitly, or if it really is only sporadic images what's wrong with [scale=.25] –  David Carlisle Feb 8 at 12:47
aetting back to 1 is a good idea. They are sporadic, all images must be scaled by the same factor. I am currently adding images as I go. If I get Overfull then I step down the scaling a notch. –  aiao Feb 8 at 12:50
@aiao scale is not the right key for solving the overfull line problems. Use width=\columnwidth or width=.9\textwidth (adjust the factor to suit). –  egreg Feb 8 at 13:46
@egreg but that would mess up the scaling ratio across images, which is imporatant in my case –  aiao Feb 8 at 13:50

Defining a private \includegraphics allows you to call macros as optional arguments:

\protected\def\newincludegraphics{\@testopt\new@includegraphics{}}
\def\new@includegraphics[#1]{%
\begingroup
\@protected@edef\x{\endgroup
\noexpand\includegraphics
\if\relax\detokenize{#1}\relax\else[#1]\fi
}\x
}

\newincludegraphics[\scalefactor]{image}

-
but if you want to do this you should probably at least use \@protected@edef rather than \edef but even then it makes the argument a "moving argument" in which fragile commands will break. The keyval parser goes to a lot of effort to avoid that, and this disables all of that mechanism. –  David Carlisle Feb 8 at 14:04
@DavidCarlisle: Thanks. Do you have examples of the possibly fragile arguments? I haven't come across them in \includegraphics. The values of keys or a file to be inserted? –  Ahmed Musa Feb 8 at 17:08
well you can go width=\ifdim\Gin@nat@width>\textwidth \textwidth \else \Gin@nat@width\fi to set the size to be natural size or textwidth, but that relies on \ifdim not being expanded during the keyval parsing and as I say the parser is designed so that it works. –  David Carlisle Feb 8 at 17:12
@DavidCarlisle: OK, thanks. I will leave the answer with \@protected@edef. Most likely the OP didn't intend to call fragile commands in the optional argument. –  Ahmed Musa Feb 8 at 20:26