Trying to do graphical decorations in "ClassicThesis style"

Question

Is there a way to obtain an effect like the page below? The gray tones of the effect in the page below are uniforms but I would have different tones among the various shapes. The main gray tone should be the following:

\definecolor{halfgray}{gray}{0.55}
\color{halfgray}% in classicthesis 

I think that, this decoration should be applied (if this experiment is successful) only at the first page of each chapter...

\documentclass[headinclude,footinclude]{scrbook}

\usepackage[eulerchapternumbers,pdfspacing]{classicthesis}

\usepackage{arsclassica}

\begin{document}
\chapter{graphic test}
\section{graphic test}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin et metus vel diam tempus egestas in ut sem. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vivamus justo orci, porttitor at tempor ut, gravida at urna. Donec facilisis purus quis dolor viverra non cursus turpis fermentum. Phasellus elit metus, interdum vitae semper id, consequat at sem. Quisque sollicitudin purus enim. Fusce ultrices libero at neque dignissim eleifend. Vestibulum est libero, accumsan vitae ullamcorper sit amet, laoreet vel mauris. Quisque id odio sapien, non ultrices justo. Nulla sit amet magna nunc, in tempor lectus. Maecenas vitae sem nec mi tincidunt vehicula.
\end{document}

---

To be clear, I wouldn't this behaviour, but I would that the decoration go always in the bigger margin... (I've have used openany)

Answer 1

Here's one possibility using TikZ; \chapterdecoration is automatically invoked using the last optional argument of \titleformat for \chapter as given in arsclassica.sty:

\documentclass[headinclude,footinclude]{scrbook}
\usepackage[eulerchapternumbers,pdfspacing]{classicthesis}
\usepackage{arsclassica}
\usepackage{tikz}
\usepackage{lipsum}

\titleformat{\chapter}[block]%
        {\normalfont\Large\sffamily}%
        {{\color{halfgray}\chapterNumber\thechapter%
        \hspace{10pt}\vline}  }{10pt}%
        {\spacedallcaps}[\chapterdecoration]

\definecolor{halfgray}{gray}{0.55}

\newcommand\chapterdecoration{%
\begin{tikzpicture}[remember picture,overlay,shorten >= -10pt]

\coordinate (aux1) at ([yshift=-15pt]current page.north east);
\coordinate (aux2) at ([yshift=-410pt]current page.north east);
\coordinate (aux3) at ([xshift=-4.5cm]current page.north east);
\coordinate (aux4) at ([yshift=-150pt]current page.north east);

\begin{scope}[halfgray!40,line width=12pt,rounded corners=12pt]
\draw
  (aux1) -- coordinate (a)
  ++(225:5) --
  ++(-45:5.1) coordinate (b);
\draw[shorten <= -10pt]
  (aux3) --
  (a) --
  (aux1);
\draw[opacity=0.6,halfgray,shorten <= -10pt]
  (b) --
  ++(225:2.2) --
  ++(-45:2.2);
\end{scope}
\draw[halfgray,line width=8pt,rounded corners=8pt,shorten <= -10pt]
  (aux4) --
  ++(225:0.8) --
  ++(-45:0.8);
\begin{scope}[halfgray!70,line width=6pt,rounded corners=8pt]
\draw[shorten <= -10pt]
  (aux2) --
  ++(225:3) coordinate[pos=0.45] (c) --
  ++(-45:3.1);
\draw
  (aux2) --
  (c) --
  ++(135:2.5) --
  ++(45:2.5) --
  ++(-45:2.5) coordinate[pos=0.3] (d);   
\draw 
  (d) -- +(45:1);
\end{scope}
\end{tikzpicture}%
}

\begin{document}

\chapter{graphic test}
\section{graphic test}
\lipsum[1-3]

\end{document}

In a comment, FormlessCloud asked for a change so that the decoration will always appear in the outer margin (this, of course, if the openany class option is active); here's the necessary modification:

\documentclass[headinclude,footinclude,openany]{scrbook}
\usepackage[eulerchapternumbers,pdfspacing]{classicthesis}
\usepackage{arsclassica}
\usepackage{tikz}
\usepackage{changepage}
\usepackage{lipsum}% just to generate text for the example

\strictpagecheck

\titleformat{\chapter}[block]%
        {\normalfont\Large\sffamily}%
        {{\color{halfgray}\chapterNumber\thechapter%
        \hspace{10pt}\vline}  }{10pt}%
        {\spacedallcaps}[\chapterdecoration]

\definecolor{halfgray}{gray}{0.55}

\newcommand\anglei{-45}
\newcommand\angleii{45}
\newcommand\angleiii{225}
\newcommand\angleiv{135}

\newcommand\chapterdecoration{%
\begin{tikzpicture}[remember picture,overlay,shorten >= -10pt]
\coordinate (aux1) at ([yshift=-15pt]current page.north east);
\coordinate (aux2) at ([yshift=-410pt]current page.north east);
\coordinate (aux3) at ([xshift=-4.5cm]current page.north east);
\coordinate (aux4) at ([yshift=-150pt]current page.north east);
\checkoddpage
\ifoddpage
\else
\coordinate (aux1) at ([yshift=-15pt]current page.north west);
\coordinate (aux2) at ([yshift=-410pt]current page.north west);
\coordinate (aux3) at ([xshift=4.5cm]current page.north west);
\coordinate (aux4) at ([yshift=-150pt]current page.north west);
\renewcommand\anglei{-135}
\renewcommand\angleii{135}
\renewcommand\angleiii{-45}
\renewcommand\angleiv{45}
\fi
\begin{scope}[halfgray!40,line width=12pt,rounded corners=12pt]
\draw
  (aux1) -- coordinate (a)
  ++(\angleiii:5) --
  ++(\anglei:5.1) coordinate (b);
\draw[shorten <= -10pt]
  (aux3) --
  (a) --
  (aux1);
\draw[opacity=0.6,halfgray,shorten <= -10pt]
  (b) --
  ++(\angleiii:2.2) --
  ++(\anglei:2.2);
\end{scope}
\draw[halfgray,line width=8pt,rounded corners=8pt,shorten <= -10pt]
  (aux4) --
  ++(\angleiii:0.8) --
  ++(\anglei:0.8);
\begin{scope}[halfgray!70,line width=6pt,rounded corners=8pt]
\draw[shorten <= -10pt]
  (aux2) --
  ++(\angleiii:3) coordinate[pos=0.45] (c) --
  ++(\anglei:3.1);
\draw
  (aux2) --
  (c) --
  ++(\angleiv:2.5) --
  ++(\angleii:2.5) --
  ++(\anglei:2.5) coordinate[pos=0.3] (d);   
\draw 
  (d) -- +(\angleii:1);
\end{scope}
\end{tikzpicture}%
}

\begin{document}

\mbox{}\newpage%just for the example
\chapter{graphic test}
\section{graphic test}
\lipsum[1-3]
\chapter{graphic test}
\section{graphic test}
\lipsum[1-3]

\end{document}

An image of the two pages containing the beginning of a chapter, illustrating the alternancy in the margin: