includegraphics and xstring package

Question

I would really like to do something like the following:

\includegraphics{\StrSubstitute{No Spaces}{ }{}}

However, this gives me an Undefined control sequence error. I saw some other posts about includegraphics not evaluating macros in arguments. So, I tried this:

\newcommand{\imageFoo}[1]{
  \includegraphics{#1}
}

\begin{document}

\imageFoo{\StrSubstitute{No Spaces}{ }{}}

\end{document}

This also gives me the Undefined control sequence error.

To test further, I defined:

\newcommand{\identityMacro}[1]{#1}

The following then all work as expected:

\includegraphics{NoSpaces}
\imageFoo{NoSpaces}
\imageFoo{\identityMacro{NoSpaces}}
\includegraphics{\identityMacro{NoSpaces}}
\StrSubstitute{No Spaces}{ }{}

Can anyone help me understand why includegraphics never works with StrSubstitute?

Answer 1

The argument has to expand to the filename.

so you can go

\newcommand\foo{file.png}
\includegraphics{\foo}

as \foo expands to file.png

But you can not go

\includegraphics{\newcommand\foo{file.png}\foo}

as the definition of the command is an assignment and not expandable. The string functions you are invoking are of this form, making internal definitions and not simply expanding to the result.

---

after

\makeatletter
\newcommand\removespace[1]{\zap@space#1 \@empty}
\makeatother

you could go

\includegraphics{\removespace{ my file}}

to input myfile.png