关于 pgf 绘图的一个问题：圆形图形

Question

例如，如何在圆形上画四个矩形，每个矩形分别压住另一个矩形？看我的图。我无法绘制左上角红色矩形后面的紫色矩形。如果你知道方法，请告诉我。

而且我想用球的颜色给形状着色，所以我不能只在左上角画一个小矩形然后将其设置为紫色。

Answer 1

在……的帮助下保罗·加博瑞特invclip可以写

\documentclass[tikz,border=2mm]{standalone}
\begin{document}

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

\begin{tikzpicture}

\fill[red] (-1,-1) rectangle (1,1);
\fill[yellow, shift={(1.5,1.5)}] (-1,-1) rectangle (1,1);
\fill[blue, shift={(3,0)}] (-1,-1) rectangle (1,1);
\begin{pgfinterruptboundingbox}
\path[invclip] (-1,-1)-|(1,1);
\end{pgfinterruptboundingbox}
\fill[purple, shift={(1.5,-1.5)}] (-1,-1) rectangle (1,1);
\end{tikzpicture}
\end{document}

Answer 2

这里用 MetaPost 完成了，同样通过裁剪和恢复交叉部分。将与 LuaLaTeX 一起运行。

我使用了 MetaPost 的 Metafun 格式提供的阴影功能。我选择了线性阴影，因为它似乎更适合矩形。

\documentclass{standalone}
\usepackage{luamplib}
    \mplibsetformat{metafun}
\begin{document}
\begin{mplibcode}
input mpcolornames;

vardef myshade(expr debut, fin, mycolor) =
    define_linear_shade(debut, fin, .1[white, mycolor], mycolor)
enddef;

def fillit_withshade(expr pat, mycolor) =
    fill pat withshade myshade(ulcorner pat, lrcorner pat, mycolor);
enddef;

beginfig(1);
    numeric a, b; a = 2.75cm; b = 3cm; 
    picture intersect; intersect = nullpicture;
    path rect[], fullrect, bb_intersect; fullrect = fullsquare xyscaled (a, b); 
    rect1 = fullrect xshifted .75a; rect2 = fullrect yshifted .75b;
    rect3 = fullrect xshifted -.75a; rect4 = fullrect yshifted -.75b;
    bb_intersect = buildcycle(rect4, subpath (3, 5) of rect1) 
        leftenlarged .5bp bottomenlarged .5bp;
        % extends the intersection to its lower-left boundary (.5bp is the default pen width)

    fillit_withshade(rect4, Purple);
    clip currentpicture to bb_intersect; addto intersect also currentpicture;
    fillit_withshade(rect4, Purple); fillit_withshade(rect3, red);
    fillit_withshade(rect2, yellow); fillit_withshade(rect1, blue);
    draw intersect;
endfig;
\end{mplibcode}
\end{document}

Answer 3

您可以简单地使用 再次绘制矩形的一部分clip。

\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
\shade[ball color=red] (-1,-1) rectangle (1,1);
\shade[ball color=yellow] (0.5,0.5) rectangle (2.5,2.5);
\shade[ball color=blue] (2,-1) rectangle (4,1);
\shade[ball color=purple] (0.5,-2.5) rectangle (2.5,-0.5);
\clip (-1,-1) rectangle (1,0);  %clip the the top half away
\shade[ball color=red] (-1,-1) rectangle (1,1); %and draw the red rectangle again
\end{tikzpicture}
\end{document}