Overlay pictures anywhere in Latex

Reproduced from https://tex.stackexchange.com/a/408447

Overlay a picture anywhere on a page (doesn't influence the original format) :

\documentclass{article}
\usepackage{graphicx,tikz}
\pagestyle{empty}
\begin{document}
\mbox{}
\begin{tikzpicture}[overlay,remember picture]
 \node[anchor=north west,inner sep=0pt]at ([xshift=1cm,yshift=-1cm]current page.north west) {\includegraphics[width=5cm]{example-image-a}};
 %only to show the values:
 \draw[red,<->] ([yshift=-1cm]current page.north west) --++ (1,0) node[midway,above]{1cm}; 
 \draw[red,<->] ([xshift=1cm]current page.north west) --++ (0,-1) node[midway,right]{1cm}; 
 \draw[red,<->] ([xshift=1cm,yshift=-3cm]current page.north west) --++ (5,0) node[midway,above]{5cm}; 
 \end{tikzpicture}
\end{document}