[Tex/LaTex] TikZ: How to draw a pattern at the border of a tikz path

patterntikz-pgf

I want to draw the shapes of airspaces according to the german VFR map style and I have problems with the restricted areas, ED-R44 in this picture:

_{(source: flightplanner.de)}

I already found out how to do the airspace A and B,C,D but the fill mechanism doesn't transpose to the hatch pattern I am looking for:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{patterns}

\tikzstyle{EDR}=[draw=red,line width=1pt,preaction={clip, postaction={pattern=north west lines, pattern color=red}}]
\tikzstyle{D}=[draw=blue,line width=1pt,preaction={clip, postaction={draw=blue,opacity=0.5,line width=12pt}}]

\begin{document}
\begin{tikzpicture}
\draw[EDR] (1,0) -- (4.5,1.5) -- (4,4) -- (1,3.5) -- (2.5,2) -- cycle;

\node at (6,2) {$\rightarrow$};

\draw[EDR] (8,0) rectangle (12,4);
\draw[fill=white,draw=none] (8.5,0.5) rectangle (11.5,3.5);

\draw[D] (13,0) rectangle (17,4);
\end{tikzpicture}
\end{document}

The problem is, that the white fill doesn't work for arbitraray polygons, but I am unable to think of a way for preaction, postaction or decoration, to make it work.

Best Answer

NEW ANSWER BASED ON YOUR OWN ANSWER: This avoids the white filling. UPDATE: One single style does the job. (I also did the blue contour.)

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{decorations,backgrounds}

\newcounter{tmp}

%\tikzstyle{D}=[draw=blue,line width=1pt,preaction={clip, postaction={draw=blue,opacity=0.5,line width=12pt}}]
%<- note that tikzstyle is deprecated

\tikzset{D/.style={
preaction={draw=blue,line width=1pt},
preaction={decoration={contour lineto closed, contour distance=6pt},
decorate,
},
postaction={
insert path={%
\pgfextra{%
\pgfinterruptpath
\begin{scope}[opacity=0.5, transparency group]
\path[fill=blue,even odd rule] 
\mySecondList \myList 
;
\end{scope}
\endpgfinterruptpath}
}},
}}



\tikzset{EDR/.style={
preaction={draw=red,line width=1pt},
preaction={decoration={contour lineto closed, contour distance=6pt},
decorate,
},
postaction={
insert path={%
\pgfextra{%
\pgfinterruptpath
\path[pattern=north west lines, pattern color=red,even odd rule] 
\mySecondList \myList 
;
\endpgfinterruptpath}
}},
}}

\makeatletter
\def\pgfdecoratedcontourdistance{0pt}
\pgfset{
  decoration/contour distance/.code=%
    \pgfmathsetlengthmacro\pgfdecoratedcontourdistance{#1}}
\pgfdeclaredecoration{contour lineto closed}{start}{%
  \state{start}[
    next state=draw,
    width=0pt,
    persistent precomputation=\let\pgf@decorate@firstsegmentangle\pgfdecoratedangle]{%
    \pgfextra{\xdef\myList{}\xdef\mySecondList{}}
    \pgfextra{\setcounter{tmp}{0}}
    \pgfpathmoveto{\pgfpointlineattime{.5}
      {\pgfqpoint{0pt}{\pgfdecoratedcontourdistance}}
      {\pgfqpoint{\pgfdecoratedinputsegmentlength}{\pgfdecoratedcontourdistance}}}%
  }%
  \state{draw}[next state=draw, width=\pgfdecoratedinputsegmentlength]{%
    \ifpgf@decorate@is@closepath@%
      \pgfmathsetmacro\pgfdecoratedangletonextinputsegment{%
        -\pgfdecoratedangle+\pgf@decorate@firstsegmentangle}%
    \fi
    \pgfmathsetlengthmacro\pgf@decoration@contour@shorten{%
      -\pgfdecoratedcontourdistance*cot(-\pgfdecoratedangletonextinputsegment/2+90)}%
    \pgfpathlineto
      {\pgfpoint{\pgfdecoratedinputsegmentlength+\pgf@decoration@contour@shorten}
      {\pgfdecoratedcontourdistance}}%
    \stepcounter{tmp}
    \pgfcoordinate{muemmel\thetmp}{\pgfpoint{\pgfdecoratedinputsegmentlength+\pgf@decoration@contour@shorten}
      {\pgfdecoratedcontourdistance}}
    \pgfcoordinate{feep\thetmp}{\pgfpoint{\pgfdecoratedinputsegmentlength}{0pt}}      
    \pgfextra{\xdef\myList{\myList (muemmel\thetmp) -- }%
        \xdef\mySecondList{\mySecondList (feep\thetmp) -- }}
    \ifpgf@decorate@is@closepath@%
      \pgfpathclose
      \pgfextra{\xdef\myList{\myList cycle}% 
      \xdef\mySecondList{\mySecondList cycle}}
    \fi
  }%
  \state{final}{\pgfextra{%\typeout{\myList,\mySecondList}
  }}%
}
\makeatother
\tikzset{
  contour/.style={
    decoration={
      name=contour lineto closed,
      contour distance=#1
    },
    decorate}}
\begin{document}

\begin{tikzpicture}
\draw(0,0) -- ({sqrt(8)},4) node[midway,sloped,above]{That's just a test!};

\path[EDR]
(1,0) -- (4.5,1.5) -- (4,4) -- (1,3.5) -- (3.5,2) -- cycle;

\path[D] (7,0) -- (9.5,2.5) -- (11,4) -- (9,3.5) -- (8,2) -- cycle;


\end{tikzpicture}

\end{document}

ORIGINAL ANSWER: Some very similar question has been answered here. Using the code written there allowed me to write a command \DrawBorder, which I believe does what you want. Note, however, that the present version works for polygons only. (EDIT: Added the BCD style, cleaned up the code and added explanations.)

\documentclass[tikz,border=3pt]{standalone}
\usetikzlibrary{patterns,decorations,calc}
%
\def\contourwidth{12pt} 
% Notice that this width enters at two places
% first it defines the widths of the nodes created by \tikzsegment
% but it also defines the overshoot, required when an angle is larger than 
% 180 degrees
\newcommand{\tikzsegment}[3][]{ % from https://tex.stackexchange.com/a/192824/121799
\path let
      \p1=($#3-#2$),
      \n1={veclen(\p1)+1.75*\contourwidth}
 in #2 -- #3 
 node[minimum width=\n1, 
         inner sep=0pt, 
         pos=0.5,sloped,rectangle,
         fill=white]{} 
    node[minimum width=\n1, 
         inner sep=0pt, 
         pos=0.5,sloped,rectangle,
         #1] 
     (line){};
}
\newcommand{\DrawBorderA}[2][]{
\begin{scope}
\foreach \point [count=\n] in {#2} {
\ifnum\n=1
\xdef\ClipList{\point --}
\else
\xdef\ClipList{\ClipList \point --}
\fi
\node (prev) at \point {};
}
\xdef\ClipList{\ClipList cycle;}%\typeout{\ClipList}
\clip \ClipList
\foreach \point in {#2} {
\node (new) at \point {};%\typeout{\point}
\tikzsegment[pattern=north west lines, pattern color=red,
               minimum height={2*\contourwidth}]
              {(prev.center)}{(new.center)}    
\node (prev) at \point {};            
}
\draw[red,line width=2pt] \ClipList                    
\end{scope}
}

\newcommand{\DrawBorderBCD}[2][]{
\begin{scope}[opacity=0.5, transparency group]
\foreach \point [count=\n] in {#2} {
\ifnum\n=1
\xdef\ClipList{\point --}
\else
\xdef\ClipList{\ClipList \point --}
\fi
\node (prev) at \point {};
}
\xdef\ClipList{\ClipList cycle;}%\typeout{\ClipList}
\clip \ClipList
\foreach \point in {#2} {
\node (new) at \point {};%\typeout{\point}
\tikzsegment[fill=blue,
               minimum height={2*\contourwidth}]
              {(prev.center)}{(new.center)}
\node (prev) at \point {};            
}             
\end{scope}
\draw[blue,opacity=1,line width=1pt] \ClipList            
s}

% \tikzstyle{EDR}=[draw=red,line width=1pt,preaction={clip, postaction={pattern=north west lines, pattern color=red}}]
% \tikzstyle{D}=[draw=blue,line width=1pt,preaction={clip, postaction={draw=blue,opacity=0.5,line width=12pt}}]
\begin{document}

\begin{tikzpicture}

\DrawBorderA{(1,0),(4.5,1.5),(4,4),(1,3.5),(2.5,2)}

\begin{scope}[xshift=5cm]
\DrawBorderBCD{(1,0),(4.5,1.5),(4,4),(1,3.5),(2.6,2)}
\end{scope}

\end{tikzpicture}
\end{document}

DISCLAIMER: It does not yet work with arbitrarily crazy angles (much larger than 270 degrees). Dealing with those will either require brute force, i.e. some fair amount of work, or some clever idea. I plan to revisit this task once I know that this is the way to go.

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] Hatch a rectangle in TikZ

You can use the library patterns. For example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{patterns}

\begin{document}
\begin{tikzpicture}
\draw[pattern=north west lines, pattern color=blue] (0,0) rectangle (2,4);
\end{tikzpicture}

\end{document}

which gives you as result:

enter image description here

You find much more in the documentation (pgfmanual): Chapter 62 Pattern Library.

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] Hatch a rectangle in TikZ

Related Question