Insert caption depending on condition

Question

I am having issues with writing a Macro. The idea is that I am trying to setup a (simple) Macro to hold the figures for an article, but not all the figures have captions and thus I want that macro to have the option to set the:

1. Source of the image (e.g., my_figure.png)
2. The width with respect to the \textwidth (e.g., 0.8 -> 80% of the text width)
3. The caption, if needed.

By using the \newcommand macro I can achieve this:

\usepackage{ifthen}
\newcommand*\tkzimage[3]{% 
\begin{figure}[h!]
\centering
\begin{tikzpicture}
    \node[inner sep=0pt] (w) at (0,0) 
    {\includegraphics[width=#2\textwidth]{images/#1}};
\end{tikzpicture}
\ifthenelse{\equal{#3}{}}{ }{\caption{#3}}
\end{figure}
}

The problem that I am having is when invoking the macro, I get the expected behavior, but the code doesn't work if I don't have \caption{<whatever>} in the empty slot:

\ifthenelse{\equal{#3}{}}{}{\caption{#3}} % Throws an error.
\ifthenelse{\equal{#3}{}}{ }{\caption{#3}} % Throws an error.
\ifthenelse{\equal{#3}{}}{<whatever>}{\caption{#3}} % Throws an error.
\ifthenelse{\equal{#3}{}}{\caption{<whatever>}>}{\caption{#3}} % Works!

The function is being invoked as:

\tkzimage{image\_text.png}{0.5}{}           # With NO caption.
\tkzimage{image\_text.png}{0.5}{Some text}  # With some caption.

I am puzzled as to why this behavior and how to solve it. The pgfkeys package is not working either, so I don't know how else to approach this; help would be appreciated.

Compiler Error

When the above code is used without the \caption code:

LaTeX Warning: `!h' float specifier changed to `!ht'.
File: images/pycharmInstallation000.png Graphic file (type png)
<use images/pycharmInstallation000.png>
Package luatex.def Info: images/pycharmInstallation000.png  used on input line 18.
(luatex.def)             Requested size: 234.73523pt x 189.33287pt.
./aaf_introduction_neovim.tex:18: Package hypcap Error: You have forgotten to use \caption.

Thanks!

Answer 1

If a caption may or may not be present, it's an optional argument.

Here I also provide for additional setting in \includegraphics and for the optional short caption for the list of figures.

Beware that \begin{figure}[!h] is wrong as it may block the queue and cause delivery of all subsequent figures at the end of the document (or chapter).

By the way, what's the tikzpicture doing?

\documentclass{article}
\usepackage{tikz}
\usepackage{graphicx}
\NewDocumentCommand{\tkzimage}{mO{}moo}{%
  \begin{figure}[!htp]% <--- not just !h, it's wrong
  \centering
  \begin{tikzpicture}
    \node[inner sep=0pt] (w) at (0,0) {%
      \includegraphics[width=#1\textwidth,#2]{#3}%
    };
  \end{tikzpicture}
  \IfValueT{#4}{% there's a caption
    \IfNoValueTF{#5}{% no short caption
      \caption{#4}%
    }{% there's a short caption
      \caption[#4]{#5}%
    }%
  }
  \end{figure}
}
\begin{document}
\listoffigures
\section{Test}
\tkzimage{0.2}{example-image-a}[A caption]
\tkzimage{0.2}{example-image-b}[Short caption for lof][A veeeeeeeeeeery long caption]
\tkzimage{0.2}[angle=90]{example-image-c}
\end{document}

Answer 2

This is the solution that I found, it is not the most elegant solution, but it works for me:

\usepackage{ifthen}
\usepackage{caption}
\newcommand*\tkzimage[3]{
\begin{figure}[h!]
\centering
\begin{tikzpicture}
\node[inner sep=0pt] (w) at (0,0) 
{\includegraphics[width=#2\textwidth]{images/#1}};
\end{tikzpicture}
\ifthenelse{\equal{#3}{}}{
    \captionsetup{labelformat=empty}
    \caption[]{}
    \addtocounter{figure}{-1}
}
{
    \caption{#3}
}
\end{figure}

} 

Notice that every time that the figure environment is called, the figure counter is increased, thus, if there is no caption added then the counter should not increase; i.e., the net increment must be zero, that is the reason why the command \addtocounter{figure}{-1} is used.