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如何绘制一个填充随机大小圆形图案的矩形？

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如何绘制一个填充随机大小圆形图案的矩形？

我希望生成一个具有圆形特征的矩形（表示水粒子），如下所示：

在此处输入图片描述

这表明入射辐射随距离增加而减小（如箭头阴影所示）。这个相当简单的示例是在 PowerPoint 中生成的，我该如何使用 tikz 绘制它。

我显然可以用以下方法绘制一个普通的矩形和箭头：

\begin{tikzpicture}
\draw (0,0) rectangle (2,1);
\draw[>=stealth, <-] (1,0) -- (1,1);
\end{tikzpicture}

但是我如何用圆圈填充矩形（如图所示），以及如何为箭头添加阴影？

答案1

Torbjørn 在评论中指出的答案是相关的，但那里的圆圈始终具有相同的半径。

另一种方法：

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{fadings,shapes.arrows,shadows}

\usepackage{xparse}

\tikzfading[name=arrowfading, top color=transparent!0, bottom color=transparent!95]
\tikzset{arrowfill/.style={#1,general shadow={fill=black, shadow yshift=-0.8ex, path fading=arrowfading}}}
\tikzset{arrowstyle/.style n args={3}{draw=#2,arrowfill={#3}, single arrow,minimum height=#1, single arrow,
single arrow head extend=.3cm,}}

\NewDocumentCommand{\tikzfancyarrow}{O{2cm} O{FireBrick} O{top color=OrangeRed!20, bottom color=Red} m}{
\tikz[baseline=-0.5ex]\node [arrowstyle={#1}{#2}{#3}] {#4};
}

% Parameters

\def\height{5}
\def\width{10}
\def\numpoints{500}
\def\maxpointwidth{1.75}

\begin{document}


\begin{tikzpicture}
\path (0,0) rectangle (\width,\height);

\foreach \point in {1,...,\numpoints}{
  \pgfmathparse{random()}
  \pgfmathsetmacro\xpos{\width*\pgfmathresult}
  \pgfmathparse{random()}
  \pgfmathsetmacro\ypos{\height*\pgfmathresult}
  \pgfmathrandom{0.1,\maxpointwidth}
  \let\pointwidth\pgfmathresult

  \node[circle,inner sep=\pointwidth pt,fill=blue!30] (point-\point) at (\xpos,\ypos) {};
}

\node [arrowstyle={\height cm}{black}{top color=orange,bottom color=yellow,shape border rotate=270}] at (\width/2,\height/2) {};

\end{tikzpicture}


\end{document}

在此处输入图片描述

这使用使用 TikZ 制作精美的箭头创建渐变，并且可以在序言中设置各种参数。

这可能是过度杀戮解决方案，但可以实现更高的定制：

\documentclass[tikz,png]{standalone}

\usepackage{tikz}
\usetikzlibrary{fadings,shapes.arrows,shadows}

\usepackage{xparse}
\newif\ifshadecircle
\pgfkeys{/tikz/.cd,
     height rect/.initial=5,
     height rect/.get=\height,
     height rect/.store in=\height,
     width rect/.initial=10,
     width rect/.get=\width,
     width rect/.store in=\width,
     num points/.initial=500,
     num points/.get=\numpoints,
     num points/.store in=\numpoints,
     point width/.initial=1.5pt,
     point width/.get=\maxpointwidth,
     point width/.store in=\maxpointwidth,
     point style type/.is choice,
     point style type/fill/.style={fill=\pointcolor},
     point style type/radial shade/.style={inner color=\pointinnercolor,outer color=\pointoutercolor},
     point style type/vertical shade/.style={top color=\pointtopcolor,bottom color=\pointbottomcolor},
     point style type/horizontal shade/.style={left color=\pointleftcolor,right color=\pointrightcolor},
     point style/.initial={/tikz/point style type/fill},
     point style/.get=\pointstyle,
     point style/.store in=\pointstyle,
     point fill color/.initial=blue!30,
     point fill color/.get=\pointcolor,
     point fill color/.store in=\pointcolor,
     point inner color/.initial=white,
     point inner color/.get=\pointinnercolor,
     point inner color/.store in=\pointinnercolor,
     point outer color/.initial=blue!30,
     point outer color/.get=\pointoutercolor,
     point outer color/.store in=\pointoutercolor,
     point top color/.initial=white,
     point top color/.get=\pointtopcolor,
     point top color/.store in=\pointtopcolor,
     point bottom color/.initial=blue!30,
     point bottom color/.get=\pointbottomcolor,
     point bottom color/.store in=\pointbottomcolor,
     point left color/.initial=blue!30,
     point left color/.get=\pointleftcolor,
     point left color/.store in=\pointleftcolor,
     point right color/.initial=white,
     point right color/.get=\pointrightcolor,
     point right color/.store in=\pointrightcolor,
     arrow top color/.initial=orange,
     arrow top color/.get=\arrowtopcolor,
     arrow top color/.store in=\arrowtopcolor,
     arrow bottom color/.initial=yellow,
     arrow bottom color/.get=\arrowbottomcolor,
     arrow bottom color/.store in=\arrowbottomcolor,
     arrow border color/.initial=black,
     arrow border color/.get=\arrowbordercolor,
     arrow border color/.store in=\arrowbordercolor,
}

\tikzfading[name=arrowfading, top color=transparent!0, bottom color=transparent!95]
\tikzset{arrowfill/.style={#1,general shadow={fill=black, shadow yshift=-0.8ex, path fading=arrowfading}}}
\tikzset{arrowstyle/.style n args={3}{draw=#2,arrowfill={#3}, single arrow,minimum height=#1, single arrow,
single arrow head extend=.15cm,}}

\pgfkeys{/tikz/random point diagram/.code={
   \path (0,0) rectangle (\width,\height);

   \foreach \point in {1,...,\numpoints}{
     \pgfmathparse{random()}
     \pgfmathsetmacro\xpos{\width*\pgfmathresult}
     \pgfmathparse{random()}
     \pgfmathsetmacro\ypos{\height*\pgfmathresult}
     \pgfmathparse{random()}
     \pgfmathsetmacro\pointwidth{\maxpointwidth*\pgfmathresult}

     \node[circle,inner sep=\pointwidth pt, \pointstyle] (point-\point) at (\xpos,\ypos) {};
   }

   \node [arrowstyle={\height cm}{\arrowbordercolor}{top color=\arrowtopcolor, bottom color=\arrowbottomcolor,shape border rotate=270}, anchor=north] at (\width/2,\height) {};
  }
}

% that's just an alias for \node
\makeatletter
\def\drawdiagram{\tikz@path@overlay{node}}
\makeatother

\begin{document}

\begin{tikzpicture}
\drawdiagram[random point diagram] at (0,0) {};
\end{tikzpicture}

\begin{tikzpicture}[height rect=4,width rect=8,
 num points=600,
 point style={/tikz/point style type/vertical shade}, 
 point top color=white,
 point bottom color=orange,
 arrow border color=violet,
 arrow top color=violet!50!magenta!80,
 arrow bottom color=magenta!20]
\drawdiagram[random point diagram] at (0,0) {};
\end{tikzpicture}

\end{document}

第一个例子使用默认值给出了上面的图片，而第二个自定义的例子：

在此处输入图片描述

答案2

循环\foreach构造\pgfmathramdominteger是你的朋友：

\documentclass{standalone}
\usepackage{tikz}

\usetikzlibrary{shapes.arrows, fadings}

\begin{document}
\begin{tikzpicture}
    \foreach \x in {1,...,300}
        {
            \pgfmathrandominteger{\a}{5}{995}
            \pgfmathrandominteger{\b}{5}{395}
            \pgfmathrandominteger{\c}{30}{60}
            \fill[shade=blue!80!white] (0.01*\a,0.01*\b) circle (0.001*\c);
        };
    \node at (5,2) [
        right color=red!80!yellow,
        left color = red!20!yellow,
        single arrow,
        single arrow head extend=0.2cm,
        single arrow tip angle=110,
        single arrow head indent=0.05cm,
        minimum height=4cm,
        inner sep=1pt,
        shading angle=90+90,
        rotate=270
    ] {};
\end{tikzpicture}
\end{document}

在此处输入图片描述

感谢 Jake 提供的链接如何绘制一个渐变填充的箭头？，我从中复制了箭头。

答案3

只是为了好玩而使用 PSTricks，这不一定是最正确的方法。请随意编辑。

在此处输入图片描述

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-grad}% for gradient
\SpecialCoor
\newpsstyle{mygradient}
{
    fillstyle=gradient,
    gradbegin=orange,
    gradend=yellow,
    %gradangle=90,
    gradmidpoint=1,
}   
\begin{document}
\begin{pspicture}(8,6)
    \psLoop{500}{\pscircle*[linecolor=blue!80!white]
        (!rand 800 mod 100 div rand 600 mod 100 div){!rand 100 mod 1000 div}}
    \pspolygon[style=mygradient](3.75,6)(3.75,1)(3.25,1)(4,0)(4.75,1)(4.25,1)(4.25,6)
\end{pspicture}
\end{document}

请注意，我假设气泡可以相互重叠。

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