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如何在 TikZ 中反转“剪辑”选择？

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如何在 TikZ 中反转“剪辑”选择？

我希望在坐标为 (A)、(B) 和 (C) 的三角形外侧画一条弧来表示反射角。

如果我想在三角形内画圆弧，我可以使用类似

\begin{scope}
\path[clip] (A) -- (B) -- (C) -- cycle;
\draw (B) circle (2mm);    % this is the little angle marker
\end{scope}

有没有一个简单的方法排除圆位于三角形内的部分，如下面的伪代码所示？

\begin{scope}
\path[magicalinverseclipcommand] (A) -- (B) -- (C) -- cycle;
\draw (B) circle (2mm);    % this is the little angle marker
\end{scope}

编辑：虽然我将上面的代码作为反向剪辑的激励示例，但我更喜欢系统地处理任何封闭路径的通用解决方案，而不仅仅是在三角形中剪辑出一个圆的特定示例中。看着我的问题，我意识到这并不清楚，我会对我的特定问题的最佳解决方案感到满意，但我想知道是否有比目前列出的解决方案更少临时的解决方案。

答案1

您可以做的是向剪切路径添加一个大于当前边界框的矩形，然后使用该矩形进行剪切。Andrew Stacey 建议使用当前页面作为剪切矩形，因为这样可以捕获后面的所有元素。通过pgfinterruptboundingbox在定义剪切矩形时使用环境，实际大小tikzpicture不会受到影响。

请注意，为了使用current page，remember picture,overlay需要将选项传递给tikzpicture，并且需要运行两次编译才能正确定位所有元素。此外，这不适用于 documentclass minimal。

\documentclass{article} % Has to be a proper class, not minimal
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[remember picture,overlay]

% A path that follows the edges of the current page
\tikzstyle{reverseclip}=[insert path={(current page.north east) --
  (current page.south east) --
  (current page.south west) --
  (current page.north west) --
  (current page.north east)}
]

\coordinate (A) at (0,0);
\coordinate (B) at (1,0);
\coordinate (C) at (1,1);

\begin{pgfinterruptboundingbox} % To make sure our clipping path does not mess up the placement of the picture
\path [clip] (A) -- (B) -- (C) -- cycle [reverseclip];
\end{pgfinterruptboundingbox}

\draw[thick] (A) circle (2mm);
\draw[thick] (B) circle (2mm);    
\draw[thick] (C) circle (2mm);   

\end{tikzpicture}
\end{document}

只是为了证明它适用于一般情况：

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[remember picture,overlay]

% A path that follows the edges of the current page
\tikzstyle{reverseclip}=[insert path={(current page.north east) --
  (current page.south east) --
  (current page.south west) --
  (current page.north west) --
  (current page.north east)}
]

\draw [step=0.1,red] (0,0) grid  (2,2);

\begin{pgfinterruptboundingbox} % To make sure our clipping path does not mess up the placement of the picture
\path [clip,rounded corners] (0,0) -- (.75,0) -- (1.2,.8) -- (2,1) -- (1.4,1) -- (1.2,2) -- (.3,.75) -- cycle [reverseclip];
\end{pgfinterruptboundingbox}

\draw [step=0.1,thick] (0,0) grid  (2,2);

\end{tikzpicture}
\end{document}

通用路径剪辑

答案2

为了避免remember picture和overlay，我使用以下方法混合 Jack 溶液和 Altermundus 溶液：大TikZ/PGF（TeX？）可以使用的矩形（编辑：正如 Qrrbrbirlbel 所建议的，我添加了[reset cm]一个独立于任何尺度变换的解决方案）。

第一个 tikzpicture 显示了两个（inv）剪辑三角形。

第二张 tikzpicture 显示的效果nonzero rule（even odd rule不能直接在剪切路径中使用，请参阅下面的注释）。

\documentclass{standalone}
\usepackage{tikz}
\begin{document}

\tikzset{invclip/.style={clip,insert path={{[reset cm]
      (-16383.99999pt,-16383.99999pt) rectangle (16383.99999pt,16383.99999pt)
    }}}}

\begin{tikzpicture}[outer sep=0mm]
  \coordinate (A) at (0,0);
  \coordinate (B) at (1,0);
  \coordinate (C) at (.5,1);
  \coordinate (Ap) at (0,1);
  \coordinate (Bp) at (1,1);
  \coordinate (Cp) at (.5,0);
  \begin{scope}
  \begin{pgfinterruptboundingbox} % useful to avoid the rectangle in the bounding box
    \path[invclip]
    (A) -- (B) -- (C) -- (A)
    (Ap) -- (Cp) -- (Bp) -- (Ap);
  \end{pgfinterruptboundingbox} 

  \fill[orange!50] (-1,-1) rectangle (2,2);

  \draw (A) circle (2mm);    % this is the little angle marker
  \draw (B) circle (2mm);    % this is the little angle marker
  \draw (C) circle (2mm);    % this is the little angle marker

  \draw (Ap) circle (2mm);    % this is the little angle marker
  \draw (Bp) circle (2mm);    % this is the little angle marker
  \draw (Cp) circle (2mm);    % this is the little angle marker

  \end{scope}

  \draw[red] (current bounding box.south west)
  rectangle (current bounding box.north east);
\end{tikzpicture}

\begin{tikzpicture}[outer sep=0mm]
  \coordinate (A) at (0,0);
  \coordinate (B) at (1,0);
  \coordinate (C) at (.5,1);
  \coordinate (Ap) at (0,1);
  \coordinate (Bp) at (1,1);
  \coordinate (Cp) at (.5,0);
  \begin{scope}
  \begin{pgfinterruptboundingbox} % useful to avoid the rectangle in the bounding box
    \path[invclip]
    (A) -- (B) -- (C) -- (A)
    (Ap) -- (Bp) -- (Cp) -- (Ap);
  \end{pgfinterruptboundingbox} 

  \fill[orange!50] (-1,-1) rectangle (2,2);

  \draw (A) circle (2mm);    % this is the little angle marker
  \draw (B) circle (2mm);    % this is the little angle marker
  \draw (C) circle (2mm);    % this is the little angle marker

  \draw (Ap) circle (2mm);    % this is the little angle marker
  \draw (Bp) circle (2mm);    % this is the little angle marker
  \draw (Cp) circle (2mm);    % this is the little angle marker

  \end{scope}

  \draw[red] (current bounding box.south west)
  rectangle (current bounding box.north east);
\end{tikzpicture}
\end{document}

在此处输入图片描述

关于规则和剪辑的注意事项：

在路径中无法组合clip和（在我看来这几乎是一个错误）。但是，如果您将选项添加到封闭范围，则操作将使用它。应用于上一个示例，剪切路径可以使用任何旋转方向：even odd ruleeven odd ruleclip

\documentclass{standalone}
\usepackage{tikz}
\tikzset{invclip/.style={clip,insert path={{[reset cm]
        (-16383.99999pt,-16383.99999pt) rectangle (16383.99999pt,16383.99999pt)}}}}
\begin{document}
\begin{tikzpicture}[outer sep=0mm]


  \coordinate (A) at (0,0);
  \coordinate (B) at (1,0);
  \coordinate (C) at (.5,1);
  \coordinate (Ap) at (0,1);
  \coordinate (Bp) at (1,1);
  \coordinate (Cp) at (.5,0);
  \begin{scope}[even odd rule]

    \begin{pgfinterruptboundingbox} % useful to avoid the rectangle in the bounding box
      \path[invclip]
      (A) -- (B) -- (C) -- (A)
      (Ap) -- (Bp) -- (Cp) -- (Ap);
    \end{pgfinterruptboundingbox} 

    \fill[orange!50] (-1,-1) rectangle (2,2);

    \draw (A) circle (2mm);    % this is the little angle marker
    \draw (B) circle (2mm);    % this is the little angle marker
    \draw (C) circle (2mm);    % this is the little angle marker

    \draw (Ap) circle (2mm);    % this is the little angle marker
    \draw (Bp) circle (2mm);    % this is the little angle marker
    \draw (Cp) circle (2mm);    % this is the little angle marker

  \end{scope}

  \draw[red] (current bounding box.south west)
  rectangle (current bounding box.north east);
\end{tikzpicture}

答案3

@Jack 发给我一个关于invclip： 3D 图形中的反向剪辑-投影问题。

这个问题显示了@PaulGaborit 的答案中的一个问题，即双括号

\tikzset{invclip/.style={clip,insert path={{[reset cm]
      (-16383.99999pt,-16383.99999pt) rectangle (16383.99999pt,16383.99999pt)
    }}}}

不限制范围reset cm。事实上，在上面链接的例子中，它占用了四个。因此，在上面的链接中，我建议使用以下代码

\tikzset{
    clip even odd rule/.code={\pgfseteorule}, % Credit to Andrew Stacey 
    invclip/.style={
        clip,insert path=
            [clip even odd rule]{
                [reset cm](-\maxdimen,-\maxdimen)rectangle(\maxdimen,\maxdimen)
            }
    }
}

完整的例子如下

\documentclass[border=9,tikz]{standalone}
\usetikzlibrary{graphs,graphs.standard}
\begin{document}

\tikzset{
    clip even odd rule/.code={\pgfseteorule}, % Credit to Andrew Stacey 
    invclip/.style={
        clip,insert path=
            [clip even odd rule]{
                [reset cm](-\maxdimen,-\maxdimen)rectangle(\maxdimen,\maxdimen)
            }
    }
}

\tikz{
    \begin{pgfinterruptboundingbox}
        \clip[invclip](1,0)--(0,1)--(0,-1)--(-1,0)--cycle;
    \end{pgfinterruptboundingbox}
    \graph{subgraph K_n[n=20,clockwise,radius=50]};
}

\end{document}

答案4

为了开始这项工作，这里有一个使用的方法fadings。我不它的缺点是，为了使它工作，必须在淡入淡出中指定一个大矩形，希望它足够大 - 我不知道如何自动化。问题是，当指定淡入淡出时，所有内容外部褪色被认为是透明的，而对于这个，人们想要一切外部清晰可见。

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{fadings}
\begin{document}

\begin{tikzfadingfrompicture}[name=fadeit]
\fill[white] (-10,-10) rectangle (10,10);
\path (0,0) coordinate (A) +(0:2) coordinate (B) +(50:2) coordinate (C);
\fill[black] (B) -- (A) -- (C) -- cycle;
\end{tikzfadingfrompicture}

\begin{tikzpicture}
\draw[path fading=fadeit,fit fading=false] (0,0) circle (1);
\end{tikzpicture}
\end{document}

它也不是那么好，因为必须从图片中分离出剪切的定义（我想知道是否可以使用remember picture...来解决这个问题）。

反向裁剪图片

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