How can I put a picture as a centered background of a minipage?

Question

I am trying to put logos in the background of minipages. I want them to have the same hight as the minipage, since it is quite short, and be horizontally centered.

To do this I have tried to combine the solutions of these two questions: background-image-for-minipage (Gets the right height but not centered or see through) using-tikz-to-position-a-background-image-in-mini-page (Centered ans see through but wrong height)

What I have come up with is this:

\documentclass{article}

\usepackage{lipsum}%
\usepackage{fullpage}%
\usepackage{tikz}%
\usepackage{graphicx}%

\newsavebox\mysavebox
\newcommand{\bgfield}[2]{
\begin{tikzpicture}
\node[inner sep=0pt,outer sep=0pt,text width=\textwidth](a){%
\kern\dimexpr-\fboxsep-\fboxrule\relax
\begin{lrbox}{\mysavebox}%
\begin{minipage}{\textwidth}
{\Large\bfseries Title}\par%
\emph{Subtitle}%
\begin{flushleft}
    #1 % \lipsum[1]
\end{flushleft}
\end{minipage}
\end{lrbox}
\sbox\mysavebox{\usebox\mysavebox}%
\mbox{\usebox\mysavebox}%
   };
\node[anchor=north ,inner sep=0pt,outer sep=0pt,opacity=0.5] at (a.north) {
\includegraphics[width=\textwidth %, height=\dimexpr\ht\mysavebox+\dp\mysavebox\relax]{#2}};
\end{tikzpicture}
}

\begin{document}

\bgfield{\lipsum[1]}{LaTeX.png}

\end{document}

If I use it this way I get the wrong height of the logo:

If I un-comment the height of the \includegraphics, so that it becomes \includegraphics[width=\textwidth, height=\dimexpr\ht\mysavebox+\dp\mysavebox\relax]{#2} the Logo simply disappears.

Any ideas on how to solve this?

Answer 1

Maybe this alternative without all the tikz stuff would be acceptable.

EDITED to provide optional width argument for minipage.

\documentclass{article}
\usepackage{lipsum}%
\usepackage{fullpage}%
\usepackage{graphicx}%
\usepackage{stackengine}
\newcommand\bgfield[3][\textwidth]{
  \setbox0=\hbox{%
    \begin{minipage}[b]{#1}
      {\Large\bfseries Title}\par%
      \emph{Subtitle}%
      \begin{flushleft}
         #2
    \end{flushleft}
    \end{minipage}%
  }
  \noindent\stackinset{c}{}{c}{}{\copy0}{\makebox[#1]{%
    \includegraphics[height=\dimexpr\ht0+\dp0\relax]{#3}}}
}
\begin{document}
\bgfield{\lipsum[1]}{example-image.jpg}

\centering\bgfield[.7\textwidth]{\lipsum[1]}{example-image.jpg}
\end{document}

Note that, as is, the bottom of the image extends to the bottom of the "g" of "dignissim". If you wanted it only to the baseline (i.e., the bottom of "rutrum"), one would instead modify the \includegraphics optional argument to [height=\ht0].

ADDENDUM

The OP comments about transparancy and making the images more watermark like. I note that, for grayscale and rgb (not cmyk) images, the decodearray parameter to \includegraphics can simulate this as well.

\documentclass{article}
\usepackage{lipsum}%
\usepackage{fullpage}%
\usepackage{graphicx}%
\usepackage{stackengine}
\newcommand\bgfield[3][\textwidth]{
  \setbox0=\hbox{%
    \begin{minipage}[b]{#1}
      {\Large\bfseries Title}\par%
      \emph{Subtitle}%
      \begin{flushleft}
         #2
    \end{flushleft}
    \end{minipage}%
  }
  \noindent\stackinset{c}{}{c}{}{\copy0}{\makebox[#1]{%
    \includegraphics[decodearray={.7 1 .7 1 .7 1},height=\dimexpr\ht0+\dp0\relax]{#3}}}
}
\begin{document}
\bgfield{\lipsum[1]}{GoogleLogo}

\centering\bgfield[.7\textwidth]{\lipsum[1]}{example-image.jpg}
\end{document}

Changing the .7's in the decodearray argument to 0 recovers the original image. Increasing towards 1 fades it completely.

Answer 2

tcolorbox offers watermark text and watermark graphics options to add a watermark behind the box contents. This watermark can be forced to occupy the box height or width while keeping aspect ratio with watermark zoom=1.0.

\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lipsum}

\newtcolorbox{myminipage}[5][]{
   blankest, 
    before upper={\Large\bfseries #4}\par\emph{#5}\par, 
    parbox=false, 
    halign=flush left,
    watermark graphics=#3, 
    watermark zoom=1.0,
    width=#2,
    #1
}

\begin{document}

\begin{myminipage}{\linewidth}{example-image}{Title}{Subtitle}
\lipsum[3]
\end{myminipage}

\begin{myminipage}{.6\linewidth}{example-image}{Title}{Subtitle}
This is a not so long minipage. This is a not so long minipage. This is a   
not so long minipage. This is a not so long minipage. This is a not so long 
minipage.
\end{myminipage}

\end{document}