renewcommand as a simple wrapper: pass all arguments and options to the underlying command

Question

I "just" want to wrap all \includegraphics commands inside a \centerline, i.e.:

\includegraphics[width=3cm, keepaspectratio]{img}

automatically replaced by

\centerline{\includegraphics[width=3cm, keepaspectratio]{img}}

So I need a macro in the preamble, but I don't know how to pass all arguments, and all options unchanged using renewcommand:

\renewcommand{\includegraphics}[1]{\includegraphics[???]{#1}}

Do I have to go through the hassle of using \ifnextchar[ myself? (example here https://tex.stackexchange.com/a/314/95423); or do I need a package?

I stress out that the number of provided optional arguments is variable, and that even solutions with xparse or etoolbox require knowing the number of options...

---

P.S: why \centerline? Because it allows images to be larger than textwidth (see this). P.P.S: Thank you for highlighting potential drawbacks of rigidly centered includegraphics, although I am mostly interested in the general way to implement this redefinition.

Answer 1

For example, you can do this:

\let\includegraphicsori=\includegraphics
\def\includegraphics#1#{\includegraphicsA{#1}}
\def\includegraphicsA#1#2{\centerline{\includegraphicsori#1{#2}}}

The optional parameter (if any) is #1, the real parameter is #2 of the \includegraphicsA.

Answer 2

I'm not sure how useful this would be. If you use \includegraphics inside a figure environment, you just specify \centering in the environment.

However, here's an implementation that also allows a nocenter option,

\documentclass{article}
\usepackage{xparse,graphicx}

\ExplSyntaxOn
\cs_set_eq:NN \plasma_includegraphics:w \includegraphics
\cs_new_protected:Nn \plasma_includegraphics:nn
 {
  \plasma_includegraphics:w [ #1 ] { #2 }
 }
\cs_generate_variant:Nn \plasma_includegraphics:nn { V }

\keys_define:nn { plasma/includegraphics }
 {
  center .bool_set:N = \l__plasma_includegraphics_center_bool,
  center .default:n = true,
  nocenter .bool_set_inverse:N = \l__plasma_includegraphics_center_bool,
  nocenter .default:n = true,
  unknown .code:n =
   \clist_put_right:Nx \l__plasma_includegraphics_options_clist
    {
     \l_keys_key_str \tl_if_empty:nF { #1 } { = \exp_not:n { #1 } }
    },
 }

\RenewDocumentCommand{\includegraphics}{sO{}m}
 {
  \clist_clear:N \l__plasma_includegraphics_options_clist
  \keys_set:nn { plasma/includegraphics } { center, #2 }
  \IfBooleanT{#1}
   {
    \keys_set:nn { plasma/includegraphics } { clip=true }
   }
  \bool_if:NTF \l__plasma_includegraphics_center_bool
   {
    \par\noindent\makebox[\columnwidth]
     {
      \plasma_includegraphics:Vn \l__plasma_includegraphics_options_clist { #3 }
     }
    \par
   }
   {
    \plasma_includegraphics:Vn \l__plasma_includegraphics_options_clist { #3 }
   }
 }

\ExplSyntaxOff

\begin{document}

\includegraphics[width=3cm,angle=30]{example-image-a}

\includegraphics*[width=5cm,viewport=0 0 72 72]{example-image-a}

\noindent
X\includegraphics[nocenter,height=2ex]{example-image-b}Y

\end{document}

Is there a simpler way? Yes, there is, but preserving the full syntax of \includegraphics is a bit of a nuisance.

\usepackage{letltxmacro} % <--- necessary

\makeatletter
\LetLtxMacro\nocenterincludegraphics\includegraphics

\protected\def\includegraphics{%
  \@ifstar{\plasma@includegraphics@clip}{\plasma@includegraphics}%
}
\newcommand\plasma@includegraphics[2][]{%
  \par\noindent
  \makebox[\columnwidth]{\nocenterincludegraphics[#1]{#2}}%
  \par
}
\newcommand\plasma@includegraphics@clip[2][]{%
  \plasma@includegraphics[clip,#1]{#2}%
}
\makeatother

You can use \nocenterincludegraphics for including something without centering.

Note. \LetLtxMacro isn't really necessary with the current definition of \includegraphics. But things change and using a simple \let might reveal disastrous if the implementation changes.