\documentclass[a4paper, 11pt]{article}
\usepackage[manual]{eurion}
\usepackage[hidelinks]{hyperref}

\title{The \texttt{eurion} package}
\author{originalsouth\\\small\texttt{https://github.com/originalsouth/EURion}}
\date{v0.1.0 \quad 2026-04-26}

\begin{document}
\maketitle

\eurion[color=yellow, size=2]%
       {[shift={(-3cm,-3cm)}]current page.north east}
\eurion[color=green,  size=2]%
       {[shift={( 3cm, 3cm)}]current page.south west}

\section{Overview}

\texttt{eurion} overlays the \emph{EURion constellation} -- the
five-circle anti-photocopy pattern from banknotes -- onto LaTeX
document pages. Three placement modes (scatter, corner, manual);
configurable color, size, density, rotation, and seed.

This is a \emph{visual reproduction only}. Modern image-editor
anti-copy features rely on Digimarc digital watermarks, not on the
EURion constellation alone, so this package will not actually prevent
photocopying or scanning.

\section{Installation}

Drop \texttt{eurion.sty} next to your \texttt{.tex} file, or into your
local \texttt{texmf} tree. The package needs \texttt{tikz},
\texttt{eso-pic}, \texttt{xkeyval}, and \texttt{xcolor}.

\section{Quick start}

\begin{verbatim}
\usepackage{eurion}                      % scatter mode, default
\usepackage[corner=top-right]{eurion}    % one mark per corner
\usepackage[manual]{eurion}              % no auto overlay
\eurion[color=orange]{current page.center}
\end{verbatim}

\section{Modes}

\begin{description}
  \item[\texttt{scatter}] (default) Pseudo-random tiling at random
    angles across every page.
  \item[\texttt{corner}] A single constellation tucked into a chosen
    corner of every page.
  \item[\texttt{manual}] No automatic overlay; the user calls
    \verb|\eurion[opts]{coord}| at the desired locations.
\end{description}

\section{Options}

\begin{tabular}{@{}lll@{}}
  \textbf{Key} & \textbf{Values} & \textbf{Default} \\\hline
  \texttt{mode}    & \texttt{scatter} \textbar{} \texttt{corner} \textbar{} \texttt{manual} & \texttt{scatter} \\
  \texttt{color}   & \texttt{yellow} \textbar{} \texttt{green} \textbar{} \texttt{orange} \textbar{} xcolor expr & banknote gold \\
  \texttt{size}    & scale factor (\texttt{1} $\approx$ 1\,mm rings) & \texttt{1} \\
  \texttt{density} & integer count per page (\texttt{scatter}) & \texttt{20} \\
  \texttt{rotate}  & \texttt{random} \textbar{} \texttt{none} \textbar{} degrees & \texttt{random} \\
  \texttt{corner}  & \texttt{top-left} \textbar{} \texttt{top-right} \textbar{} \texttt{bottom-left} \textbar{} \texttt{bottom-right} & \texttt{top-right} \\
  \texttt{seed}    & integer & \texttt{1} \\
\end{tabular}

\section{The \texttt{\textbackslash eurion} macro}

In any mode you can drop an extra constellation by hand:
\begin{verbatim}
\eurion[color=green, size=2, rotate=15]{current page.center}
\eurion[color=orange]{[shift={(3cm,-3cm)}]current page.north west}
\end{verbatim}
The argument is any TikZ coordinate; the macro draws inside its own
\texttt{remember picture, overlay} \texttt{tikzpicture}.

\section{Caveats}

\begin{itemize}
  \item \textbf{Color channel only.} Detection software looks for the
    rings in a color channel; a B\&W print of your PDF will hide the
    pattern.
  \item \textbf{Not real anti-copy.} See above; this is decorative.
  \item \textbf{The exact spec is secret.} Public reproductions
    disagree on coordinates; this package uses the geometry from
    Petr Kutalek's PostScript gist.
\end{itemize}

\section{License}

WTFPL, see the \texttt{LICENSE} file. The author does not endorse this
license; it was picked because CTAN requires a license to be selected.

\section{References}

\begin{itemize}\setlength{\itemsep}{0pt}
  \item \url{https://en.wikipedia.org/wiki/EURion_constellation}
  \item \url{https://www.cl.cam.ac.uk/~mgk25/eurion.pdf}
  \item \url{https://gist.github.com/petrkutalek/93b7eebf22f4dbcfab8cd80a91fd27a8}
  \item \url{https://murdoch.is/projects/currency/}
\end{itemize}

\end{document}
