Can I place a caption inside of an image?

Question

I've recently seen this the following image in this question:

As I was looking for a way to create nice captions (without the "Figure:") for a beamer presentation, I wondered if it was possible to create this effect within LaTeX.

I got so far with GIMP:

I did it like this:

1. add a white layer where the caption will go and set it's transparancy to 50%
2. gaussian blur on the image where the caption will go 3 add the caption

Can I do this within LaTeX, too?

I have a couple of images which I would like to include in a beamer presentation like this, so it would be great if this worked.

(I've tried a google image search for this, but "latex caption" seems not to be good ... even when I filter explicit results)

My try:

\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}

\usepackage{tikz}

\begin{document}
\begin{preview}
    \begin{tikzpicture}
        \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=\linewidth]{foto-martin.jpg}};
        \begin{scope}[x={(image.south east)},y={(image.north west)}]
            \draw[white, fill=white!50!transparent] (0,0.05) rectangle (1,0.1);
            \node at (0.5, 0.075) {\Huge Martin};
        \end{scope}
    \end{tikzpicture}
\end{preview}
\end{document}

But I don't know how to get the transparency / positioning working.

As somebody suggested imagemagick, I tried this:

width=`identify -format %w foto-martin.jpg`;     convert         -background '#0008'         -fill white         -gravity center         -size ${width}x40             caption:"Martin"             foto-martin.jpg +swap         -gravity south         -geometry +0+10        -composite  out.jpg

But I can't get some padding for the text in the caption and the box arround.

Answer 1

Assuming that this question isn't a duplicate of Drawing on an image with TikZ you can achieve what you want by using the opacity=<value> key, where value can be anything between 0 (invisible) and 1 (completely visible).

Complete MWE

\documentclass{beamer}

\usepackage{tikz}

\begin{document}
    \begin{tikzpicture}
        \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=\linewidth]{mushroom}};
        \begin{scope}[x={(image.south east)},y={(image.north west)}]
            \draw[white, fill=gray,opacity=0.5] (0,0) rectangle (1,0.15);
            \node[opacity=0.5] at (0.5, 0.075) {\Huge Mushroom};
        \end{scope}
    \end{tikzpicture}
\end{document}

Answer 2

Here's an approach that uses ImageMagick to blur the image and place a clipped version on top of the unblurred image (which requires -shell-escape or -enable-write18 to call the external program). The whole thing is wrapped in a macro called \labelimage{<file name>}{<image width>}{<label text>}. The background rectangle style can be set using image label background/.style, the label node uses image label text/.style:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}

\tikzset{
    image label text/.style={
        white, font=\sffamily
    },
    image label background/.style={
        white, opacity=0.35
    }
}
\newcommand{\labelimage}[3]{
    \begin{tikzpicture}
        \immediate\write18{convert #1 -blur 0x3 blurred#1}
        \node [inner sep=0pt] (original) {\includegraphics[#2]{#1}};
        \begin{scope}[
            fill=white,
            shift=(original.south west),
            x=(original.south east),
            y=(original.north west)
        ]
        \fill [clip] (0,0.05) rectangle (1,0.25);
            \node [inner sep=0pt, anchor=south west] {\includegraphics[#2]{blurred#1}};
            \fill [image label background] (0,0.05) rectangle (1,0.25)
                node [text opacity=1, pos=0.5, image label text] {#3};
        \end{scope}
    \end{tikzpicture}
}
\labelimage{martin.jpg}{width=4em}{Martin}

\end{document}