Color an example-image

Question

Is there a simple way to set the color for a (blank) example-image?

The naive way doesn't work:

\begin{figure}
\color{red}
\includegraphics[width=\textwidth]{example-image}
\color{black}
\end{figure}

I certainly don't want to have to create and store lots of colored example images and insert each individually. It also makes it awkward being forced to store multiple copies for different document environments or futz with image file paths.

As background: I will use this for categorizing and prioritizing figures to be inserted later (e.g., red = landscape photo, green = portrait painting, blue = computer diagram, orange = figure to be computed, yellow = figure to be purchased....).

Answer 1

This makes colored rectangles if the argument to \includegraphics is a declared color. In the part

\prop_gset_from_keyval:Nn \g_stork_ig_ratios_prop
 {
  red=3/4, green=16/9, blue=3/4, orange=3/4, yellow=3/4
 }

you set both the known color and the aspect ratio for the corresponding type of image (height/width).

Example of usage. The complicated code could well stay in a separate file that you \input and when all images are filled in you can remove the \input line.

\documentclass{article}
\usepackage{graphicx,xcolor}
% to be removed when the document has all the pictures
\NewCommandCopy{\originalincludegraphics}{\includegraphics}
\ExplSyntaxOn
\RenewDocumentCommand{\includegraphics}{O{}m}
 {
  \stork_ig:nn { #1 } { #2 }
 }
\prg_generate_conditional_variant:Nnn \clist_if_in:Nn { Nx } { T,F,TF }
\prop_new:N \g_stork_ig_ratios_prop
\clist_new:N \g_stork_ig_colors_clist
\keys_define:nn { stork/ig }
 {
  width .dim_set:N = \l_stork_ig_wd_dim,
  width .initial:n = 8cm,
  unknown .code:n = {},
 }
\cs_new_protected:Nn \stork_ig:nn
 {
  \group_begin:
  \clist_if_in:NxTF \g_stork_ig_colors_clist { \tl_to_str:n { #2 } }
   {
    \keys_set:nn { stork/ig } { #1 }
    \stork_ig_fake:n { #2 }
   }
   {
    \originalincludegraphics[#1]{#2}
   }
  \group_end:
 }
\cs_new_protected:Nn \stork_ig_fake:n
 {
  \textcolor{#1}
   {
    \rule
     {% width
      \l_stork_ig_wd_dim
     }
     {% height
      \dim_eval:n { \l_stork_ig_wd_dim * \prop_item:Nn \g_stork_ig_ratios_prop { #1 } }
     }
   }
 }
% set the known colors
\prop_gset_from_keyval:Nn \g_stork_ig_ratios_prop
 {
  red=3/4, green=16/9, blue=3/4, orange=3/4, yellow=3/4
 }
\prop_map_inline:Nn \g_stork_ig_ratios_prop
 {
  \clist_gput_right:Nn \g_stork_ig_colors_clist { #1 }
 }
\ExplSyntaxOff
% end of temporary code
\begin{document}
\includegraphics[width=0.4\textwidth]{red}
\includegraphics[width=0.2\textwidth]{green}
\includegraphics[width=0.2\textwidth]{orange}
\includegraphics[width=0.4\textwidth]{example-image}
\end{document}

If you don't want fixed aspect ratios for the various colors, you can modify the code to calls such as

\includegraphics[width=0.3\textwidth]{red:3/4}

where the aspect ratio is always height/width, but a single integer is allowed (with /1 implied).

\documentclass{article}
\usepackage{graphicx,xcolor}
% to be removed when the document has all the pictures
\NewCommandCopy{\originalincludegraphics}{\includegraphics}
\ExplSyntaxOn
\RenewDocumentCommand{\includegraphics}{O{}m}
 {
  \stork_ig:nn { #1 } { #2 }
 }
\prg_generate_conditional_variant:Nnn \clist_if_in:Nn { Nx } { T,F,TF }
\cs_generate_variant:Nn \seq_set_split:Nnn { NV }
\seq_new:N \l_stork_ig_name_seq
\clist_new:N \g_stork_ig_colors_clist
\keys_define:nn { stork/ig }
 {
  width .dim_set:N = \l_stork_ig_wd_dim,
  width .initial:n = 8cm,
  unknown .code:n = {},
 }
\cs_new_protected:Nn \stork_ig:nn
 {
  \group_begin:
  \seq_set_split:NVn \l_stork_ig_name_seq \c_colon_str { #2 }
  \clist_if_in:NxTF \g_stork_ig_colors_clist { \seq_item:Nn \l_stork_ig_name_seq { 1 } }
   {
    \keys_set:nn { stork/ig } { #1 }
    \stork_ig_fake:xx
     { \seq_item:Nn \l_stork_ig_name_seq { 1 } }
     { \seq_item:Nn \l_stork_ig_name_seq { 2 } }
   }
   {
    \originalincludegraphics[#1]{#2}
   }
  \group_end:
 }
\cs_new_protected:Nn \stork_ig_fake:nn
 {
  \textcolor{ #1 }
   {
    \rule
     {% width
      \l_stork_ig_wd_dim
     }
     {% height
      __stork_ig_height:n { #2 }
     }
   }
 }
\cs_generate_variant:Nn \stork_ig_fake:nn { xx }
\cs_new:Nn __stork_ig_height:n
 {
  \dim_eval:n
   {
    \l_stork_ig_wd_dim
    * 
    \tl_if_blank:nTF { #1 } { 3/4 } { #1 }
   }
 }
% set the known colors
\clist_gset:Nn \g_stork_ig_colors_clist { red, green, blue, orange, yellow }
\ExplSyntaxOff
% end of temporary code
\begin{document}
\includegraphics[width=0.4\textwidth]{red:3/4}
\includegraphics[width=0.2\textwidth]{green:16/11}
\includegraphics[width=0.2\textwidth]{orange:1}
\includegraphics[width=0.4\textwidth]{example-image}
\end{document}

Answer 2

The following approach

• Adds the option color to the list of keys for \includegraphics (default is red);

• Assumes that your "substitute" image is given by example-image.

If you supply example-image, a box of colour color that matches the dimensions set with \includegraphics is placed. Anything other than example-image is set as needed (even with a color specification).

\documentclass{article}
\usepackage{xcolor,graphicx}
\makeatletter
\define@key{Gin}{color}{\def\Gin@color{#1}}
\setlength{\fboxsep}{0pt}% Remove \fbox separation
\let\oldincludegraphics\includegraphics
\renewcommand{\includegraphics}[2][]{%
  \ifnum\pdfstrcmp{#2}{example-image}=0%
    \begingroup
      \setkeys{Gin}{color=red,#1}% Default color is red
      \colorbox{\Gin@color}{\phantom{\oldincludegraphics[#1]{#2}}}%
    \endgroup
  \else
    \oldincludegraphics[#1]{#2}%
  \fi
}
\makeatother
\begin{document}
\includegraphics[width=3em,height=4em,color=red]{example-image}
\includegraphics[width=3em,height=4em,color=red]{example-image-a}
\end{document}