This may (or may not) serve the purpose of overlapping images with text along either the top or bottom (not sides). However, because it uses opacity and the page is typeset in order of occurrence, the appearance of overlapped top will slightly differ from overlapped bottom. In particular, text overlapping the bottom of the image, because it is placed on top, will be fully dark. Text overlapping the top, because it is under the image, will be a little washed out with opacity.
The macro I provide is
\overlap{<top overlap>}{<bottom overlap>}{<content>}
The MWE:
\documentclass{article}
\usepackage{graphicx,lipsum,tikz}
\newcommand\overlap[3]{%
\setbox0=\hbox{\raisebox{-\dimexpr#2}{#3}}%
\dp0=0pt\relax
\ht0=\dimexpr\ht0-#1\relax
\begin{tikzpicture}
\node[opacity=.4]{\copy0};
\end{tikzpicture}
}
\begin{document}
\lipsum[1]
\centerline{%
\overlap{0pt}{20pt}{\includegraphics[height=60pt]{example-image}}%
}
\lipsum[2]
\centerline{%
\overlap{20pt}{0pt}{\includegraphics[height=60pt]{example-image}}%
}
\lipsum[3]
\end{document}
