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TikZ：如何在未封闭的 tikz 路径的边界上绘制图案

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TikZ：如何在未封闭的 tikz 路径的边界上绘制图案

“根据提供的解决方案TikZ：如何在 tikz 路径的边界上绘制图案我能够完成论文中的所有图形，除了一个形状。正如您在图中看到的”（;-)填充规则和边框图案）

在此处输入图片描述

我想画一个开放的路径，其中的开始和结束不相连，如情况 c) 所示，只是我想用图案来装饰它，如情况 a) 和 b) 所示。目前，我尝试通过用白色矩形隐藏路径的一部分来帮助自己。问题是我只能将图案应用于封闭的路径。一旦我删除具有样式cycle的路径末尾的EDR，EDO我就会收到错误：Package tikz Error: Cannot parse this coordinate.

如何用图案装饰开放路径？如下图所示（使用 inkscape 修改）。

在此处输入图片描述

妇女权利委员会：

\documentclass[tikz]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{decorations,backgrounds}

% BEGIN from https://tex.stackexchange.com/a/419558/11820
\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}}
% END from https://tex.stackexchange.com/a/419558/11820

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

\begin{tikzpicture}[]
  \node at (-.5,0) {a)};
  \path [EDO] (2.875,0) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75) -- cycle;
  \path [EDR] (0,0) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0) -- cycle ;
  \fill [white] (.21,.3) rectangle (2.655,-.3);

  \begin{scope}[yshift=-2cm]
  \node at (-.5,0) {b)};
    \path [EDO] (2.875,0) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75) -- cycle;
    \path [EDR] (0,0) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0) -- cycle ;
  \end{scope}

  \begin{scope}[yshift=-4cm]
    \node at (-.5,0) {c)};
    \path [draw, orange, line width=1pt] (2.875,0) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75);
    \path [draw, red, line width=1pt] (0,0) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0);
  \end{scope}
\end{tikzpicture}

\end{document}

答案1

这是执行该操作的代码的概括。它区分了封闭路径和非封闭路径。

\documentclass[tikz]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{decorations,backgrounds}

% BEGIN from https://tex.stackexchange.com/a/419558/11820
\newcounter{tmp}
\newif\ifpathisclosed

%\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]{%
    %\xdef\myList{}\xdef\mySecondList{}%
    \setcounter{tmp}{0}%
    \global\pathisclosedfalse%
    \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\number\value{tmp}}{\pgfpoint{\pgfdecoratedinputsegmentlength+\pgf@decoration@contour@shorten}
    {\pgfdecoratedcontourdistance}}%
    \pgfcoordinate{feep\number\value{tmp}}{\pgfpoint{\pgfdecoratedinputsegmentlength}{0pt}}%      
    \ifnum\value{tmp}=1\relax%
     \pgfcoordinate{muemmel0}{\pgfpoint{0pt}{\pgfdecoratedcontourdistance}}%
     \pgfcoordinate{feep0}{\pgfpoint{0pt}{0pt}}%      
     \xdef\myList{(muemmel\number\value{tmp})}%
     \xdef\mySecondList{(feep\number\value{tmp})}%
    \else
     \xdef\myList{\myList -- (muemmel\number\value{tmp})}%
     \xdef\mySecondList{(feep\number\value{tmp}) -- \mySecondList}%
    \fi 
    \ifpgf@decorate@is@closepath@%
      \pgfpathclose
      \global\pathisclosedtrue%
    \fi
  }%
  \state{final}{%\typeout{\myList,\mySecondList}%
    \ifpathisclosed%
      \xdef\myList{\myList -- cycle}% 
      \xdef\mySecondList{\mySecondList -- cycle}%
      %\typeout{closed \mySecondList \myList }
    \else
      %\typeout{\number\value{tmp}}%
      \xdef\myList{(muemmel0) -- \myList -- cycle}% 
      \xdef\mySecondList{\mySecondList -- (feep0) --}%
      %\typeout{not closed \mySecondList \myList }%   
    \fi
  }%
}
\makeatother
\tikzset{
  contour/.style={
    decoration={
      name=contour lineto closed,
      contour distance=#1
    },
decorate}}
% END from https://tex.stackexchange.com/a/419558/11820

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

\begin{tikzpicture}[]
  \path [EDO] (2.875,3) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75) -- cycle;
  \path [EDR] (0,3) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0) -- cycle ;
  \fill [white] (.21,3.3) rectangle (2.655,2.7);

  \begin{scope}[yshift=-2cm]
    \path [EDO] (2.875,3) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75) -- cycle;
    \path [EDR] (0,3) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0) -- cycle ;
  \end{scope}

  \begin{scope}[yshift=-4cm]
    \path [EDO,draw, orange, line width=1pt] (2.875,3) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75);
    \path [EDR,draw, red, line width=1pt] (0,3) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0);
  \end{scope}

  \begin{scope}[yshift=-6cm]
    \path [EDO,draw, orange, line width=1pt] (2.875,3) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75);
    \path [EDR,draw, red, line width=1pt,shorten >=6pt] (0,3) -- ++(0,-1) -- ++(6,0) -- ++(0,1) 
    -- ++(-3.125cm-6pt,0);
  \end{scope}
\end{tikzpicture}

\end{document}

在此处输入图片描述

从顶部开始数，第三条（或倒数第二条）路径是默认得到的。这是因为该路径不知道另一条路径是什么。要生成所需的输出，必须使用shorten，参见第四张（或最后一张图片）。

这是一个更加精简的版本。

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{patterns,decorations}

% BEGIN from https://tex.stackexchange.com/a/419558/11820


\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
\newif\ifdeco@path@is@closed
\newcounter{deco@count}

\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]{%
    %\xdef\myList{}\xdef\mySecondList{}%
    \setcounter{deco@count}{0}%
    \global\deco@path@is@closedfalse%
    \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{deco@count}%
    \pgfcoordinate{muemmel\number\value{deco@count}}{\pgfpoint{\pgfdecoratedinputsegmentlength+\pgf@decoration@contour@shorten}
    {\pgfdecoratedcontourdistance}}%
    \pgfcoordinate{feep\number\value{deco@count}}{\pgfpoint{\pgfdecoratedinputsegmentlength}{0pt}}%      
    \ifnum\value{deco@count}=1\relax%
     \pgfcoordinate{muemmel0}{\pgfpoint{0pt}{\pgfdecoratedcontourdistance}}%
     \pgfcoordinate{feep0}{\pgfpoint{0pt}{0pt}}%      
     \xdef\myList{(muemmel\number\value{deco@count})}%
     \xdef\mySecondList{(feep\number\value{deco@count})}%
    \else
     \xdef\myList{\myList -- (muemmel\number\value{deco@count})}%
     \xdef\mySecondList{(feep\number\value{deco@count}) -- \mySecondList}%
    \fi 
    \ifpgf@decorate@is@closepath@%
      \pgfpathclose
      \global\deco@path@is@closedtrue%
    \fi
  }%
  \state{final}{%\typeout{\myList,\mySecondList}%
    \ifdeco@path@is@closed%
      \xdef\myList{\myList -- cycle}% 
      \xdef\mySecondList{\mySecondList -- cycle}%
      %\typeout{closed \mySecondList \myList }
    \else
      %\typeout{\number\value{deco@count}}%
      \xdef\myList{(muemmel0) -- \myList -- cycle}% 
      \xdef\mySecondList{\mySecondList -- (feep0) --}%
      %\typeout{not closed \mySecondList \myList }%   
    \fi
  }%
}
\makeatother
\tikzset{
  contour/.style={
    decoration={
      name=contour lineto closed,
      contour distance=#1
    },
decorate}}
% END from https://tex.stackexchange.com/a/419558/11820

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

\begin{tikzpicture}[]
    \path [EDO,draw, orange, line width=1pt] (2.875,3) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75);
    \path [EDR,draw, red, line width=1pt,shorten >=6pt-\pgflinewidth/2] (0,3) -- ++(0,-1) -- ++(6,0) -- ++(0,1) 
    -- ++(-3.125cm-6pt,0);
\end{tikzpicture}

\end{document}

在此处输入图片描述

我做了一些清理。但是，有一件事我没有做：停止使用\pgfextra路径。这是应该避免的事情。在这种情况下，它看起来确实没问题。你也可以写一个更干净的版本，但这需要你为模式添加一个额外的命令。如果你希望把这个写出来，请告诉我。

答案2

一种方法是从装饰中去除部分draw，然后在装饰完成后画出线条，如第三个例子。

我修改了你的 MWE：

\documentclass[tikz]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{decorations,backgrounds}

% BEGIN from https://tex.stackexchange.com/a/419558/11820
\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},    %<- remove this line
    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}}
% END from https://tex.stackexchange.com/a/419558/11820

\tikzset{EDO/.style={
  %  preaction={draw=orange,line width=1pt},    %<- remove this line
    preaction={decoration={contour lineto closed, contour distance=6pt},
      decorate,
    },
    postaction={
      insert path={%
        \pgfextra{%
          \pgfinterruptpath
          \path[pattern=north east lines, pattern color=orange,even odd rule] 
          \mySecondList \myList 
          ;
        \endpgfinterruptpath}
    }},
}}
\begin{document}

\begin{tikzpicture}[]
  \node at (-.5,0) {a)};
  \path [EDO] (2.875,0) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75) -- cycle;
  \path [EDR] (0,0) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0) -- cycle ;
  \fill [white] (.21,.3) rectangle (2.655,-.3);
  \path [draw, orange, line width=1pt] (2.875,0) -- ++(0,.75) -- ++(-2.875,0) -- ++(0,-.75);
  \path [draw, red, line width=1pt] (0,0) -- ++(0,-1) -- ++(6,0) -- ++(0,1) -- ++(-3.125,0);
\end{tikzpicture}

\end{document}

由此得出以下结论 在此处输入图片描述

答案3

我注意到上面的代码必然很长很复杂，所以我使用普通的 TikZ。参数的含义很明确，您可以根据需要更改颜色。

even odd rule图案的填充选项north west lines可以完成该工作。

在此处输入图片描述

\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{patterns}
\begin{document}
\begin{tikzpicture}[thick,declare function={a=3;b=1.2;c=3.5;d=1;m=.2;}]
\path 
(0,0)   coordinate (A) +(m,m)   coordinate (At)
(a,b+d) coordinate (B) +(-m,-m) coordinate (Bt)
(a+c,b) coordinate (C) +(-m,-m) coordinate (Ct)
;
\draw[blue,pattern=north west lines,pattern color=red!50,even odd rule] 
(A)|-(B)|-(C)|-cycle (At)|-(Bt)|-(Ct)|-cycle;
\end{tikzpicture}
\end{document}

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