%This command draw either the escher knot (the original image)
%or the escher impossible brick (the new one).
%
%The Macro use the global (to the page 10) toggle "OriginalImage"
%
%The macro has one parameter:
% 1) The size to use to typeset the content
\newcommand\TTenDisplayImage[1]{%
\parbox[t]{#1}{%
\iftoggle{OriginalImage}{%
\vfill
\iftoggle{DVIOutput}{%
\centerline{\includegraphics[viewport=0 0 135 125]{escher.ps}}%
}{%
\centerline{\includegraphics[viewport=0 0 135 125]{escher.pdf}}%
}%
}{%
% Author: Julien Cretel
% Date: 24/02/2013
%
%The code was published here:
%
http://www.texample.net/tikz/examples/escher-brick-penrose-triangle/
%
\savebox\ImpossibleBrick{%
\begin{tikzpicture}[scale=4, line join=bevel]
% \a and \b are two macros defining characteristic
% dimensions of the impossible brick.
\pgfmathsetmacro{\a}{0.18}
\pgfmathsetmacro{\b}{1.37}
\tikzset{%
apply style/.code={\tikzset{##1}},
brick_edges/.style={thick,draw=black},
face_colourA/.style={fill=gray!50},
face_colourB/.style={fill=gray!25},
face_colourC/.style={fill=gray!90},
}
\foreach \theta/\v/\facestyleone/\facestyletwo in {%
0/0/{brick_edges,face_colourA}/{brick_edges,face_colourC},
180/-\a/{brick_edges,face_colourB}/{brick_edges,face_colourC}
}{
\begin{scope}[rotate=\theta,shift={(\v,0)}]
\draw[apply style/.expand once=\facestyleone]
({-.5*\b},{1.5*\a}) --
++(\b,0) --
++(-\a,-\a) --
++({-\b+2*\a},0) --
++(0,-{2*\a}) --
++(\b,0) --
++(-\a,-\a) --
++(-\b,0) --
cycle;
\draw[apply style/.expand once=\facestyletwo]
({.5*\b},{1.5*\a}) --
++(0,{-2*\a}) --
++(-\a,0) --
++(0,\a) --
cycle;
\end{scope}
}
\end{tikzpicture}}
\par
\centerline{\usebox\ImpossibleBrick}
}
}
}
