%
% apfel.tex
%
% (c) 2021 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
%
\documentclass[tikz]{standalone}
\usepackage{times}
\usepackage{amsmath}
\usepackage{txfonts}
\usepackage[utf8]{inputenc}
\usepackage{graphics}
\usetikzlibrary{arrows,intersections,math}
\usepackage{ifthen}
\begin{document}

\newboolean{showgrid}
\setboolean{showgrid}{false}
\def\breite{7}
\def\hoehe{4}

\input{eulerpath.tex}

\begin{tikzpicture}[>=latex,thick]

% Povray Bild
\begin{scope}
\clip(-0.6,-0.6) rectangle (7,6);
\node at (3.1,2.2) [rotate=-3] {\includegraphics[width=9.4cm]{apfel.jpg}};
\end{scope}

% Gitter
\ifthenelse{\boolean{showgrid}}{
\draw[step=0.1,line width=0.1pt] (-\breite,-\hoehe) grid (\breite, \hoehe);
\draw[step=0.5,line width=0.4pt] (-\breite,-\hoehe) grid (\breite, \hoehe);
\draw                            (-\breite,-\hoehe) grid (\breite, \hoehe);
\fill (0,0) circle[radius=0.05];
}{}

\draw[color=gray!50] (0,0) rectangle (4,4);
\draw[->] (-0.5,0) -- (7.5,0) coordinate[label={$C(t)$}];
\draw[->] (0,-0.5) -- (0,6.0) coordinate[label={left:$S(t)$}];
\begin{scope}[scale=8]
\draw[color=red,opacity=0.5,line width=1.4pt] \fresnela;
\end{scope}

\end{tikzpicture}

\end{document}