Use "default" figure if file is missing?

Question

I was recently in charge of organizing all of the references and labels in a very large scientific proposal document. My workflow typically involved compiling the document, seeing a "There were undefined references." statement, and then searching the resultant PDF file for the usual "?" or "??."

Sometimes those missing references were in regard to labels for figures that were used throughout the text and not something in our bibliography. It got me wondering:

Is it possible to have a "dummy" or "default" figure to use in \includegraphics statements if the requested file is missing?

Perhaps a use case would be if in the LaTeX document there were a command such as \includegraphics{scaling.pdf}, but scaling.pdf doesn't exist in the current directory, so we use the existing dummy.pdf automatically. I assume this involves renewcommand'ing the includegraphics command, but how should one go about doing it for this scenario?

Answer 1

Try the standard command \IfFileExists. It has three arguments: the file name, what to do if it exists, and what to do if it does not:

\IfFileExists{scaling.pdf}{\includegraphics{scaling.pdf}}{\includegraphics{dummy.pdf}}

Of course, you can add syntactic sugar to this:

\newcommand{\includegraphicsmaybe}[1]{\IfFileExists{#1}{\includegraphics{#1}}{\includegraphics{dummy.pdf}}}

Answer 2

The last macro called within graphicx) before including the image is \Gin@ii. Due to the structure of \Gin@ii, it is possible to patch this command and temporarily remove LaTeX error-producing capability. Here's a minimal example:

\documentclass{article}
\usepackage{etoolbox}% http://ctan.org/pkg/etoolbox
\usepackage{graphicx}% http://ctan.org/pkg/graphicx
\newcommand{\noimage}{%
  \setlength{\fboxsep}{-\fboxrule}%
  \fbox{\phantom{\rule{150pt}{100pt}}}% Framed box
}

\makeatletter
\patchcmd{\Gin@ii}
  {\begingroup}% <search>
  {\begingroup\renewcommand{\@latex@error}[2]{\noimage}}% <replace>
  {}% <success>
  {}% <failure>
\makeatother

\begin{document}
\includegraphics[width=150pt]{tiger} \par
\includegraphics[width=150pt]{tigers}
\end{document}

In the above example, the command \noimage is used to represent the output that is generated when no image exists. You could, for example, define \noimage using

\newcommand{\noimage}{\includegraphics{dummy}}

if you wish to include dummy instead of my 150pt x 100pt empty rectangle. The redefinition of \@latex@error (which takes 2 arguments that is gobbles and replaces with \noimage) occurs inside a group, making it local and is therefore reverted back after \Gin@ii finishes.

Here is the final macro called within \Gin@ii called \Ginclude@graphics; I've highlighted the part that is indirectly affected by the redefinition of \@latex@error:

\def\Ginclude@graphics#1{%
  \begingroup
  \let\input@path\Ginput@path
  \filename@parse{#1}%
  \ifx\filename@ext\relax
    \@for\Gin@temp:=\Gin@extensions\do{%
      \ifx\Gin@ext\relax
        \Gin@getbase\Gin@temp
      \fi}%
  \else
    \Gin@getbase{\Gin@sepdefault\filename@ext}%
    \ifx\Gin@ext\relax
       \@warning{File `#1' not found}%
       \def\Gin@base{\filename@area\filename@base}%
       \edef\Gin@ext{\Gin@sepdefault\filename@ext}%
    \fi
  \fi
    \ifx\Gin@ext\relax
         \@latex@error{File `#1' not found}% <----------------------------- MODIFIED
         {I could not locate the file with any of these extensions:^^J% <-- MODIFIED
          \Gin@extensions^^J\@ehc}% <-------------------------------------- MODIFIED
    \else
       \@ifundefined{Gin@rule@\Gin@ext}%
         {\ifx\Gin@rule@*\@undefined
            \@latex@error{Unknown graphics extension: \Gin@ext}\@ehc
          \else
            \expandafter\Gin@setfile\Gin@rule@*{\Gin@base\Gin@ext}%
           \fi}%
         {\expandafter\expandafter\expandafter\Gin@setfile
             \csname Gin@rule@\Gin@ext\endcsname{\Gin@base\Gin@ext}}%
    \fi
  \endgroup}

The advantage with this approach is that you don't have to modify any of your existing macro definitions, like \includegraphics. It would be possible to extend this to indicate the offending (missing) file as well.

Answer 3

Based on the other answers, I have come up with the following code to ignore missing image files in a latex document.

The advantage of this answer over the others is that it deals with the optional arguments of \includegraphics, it doesn't require a dummy.pdf file and it doesn't require changing any of the \includegraphics commands in the body of the document.

% deal with missing images which are not directly included in the repository
\newcommand{\noimage}{%
  \setlength{\fboxsep}{-\fboxrule}%
  \fbox{\phantom{\rule{10pt}{10pt}}File missing\phantom{\rule{10pt}{10pt}}}% Framed box
}
\let\includegraphicsoriginal\includegraphics
\renewcommand{\includegraphics}[2][width=\textwidth]{\IfFileExists{#2}{\includegraphicsoriginal[#1]{#2}}{\noimage}}