当我绘制轮廓时，我想知道如何使箭头沿着曲线弯曲decoration。请参阅下面的示例。
这是我的 MWE：
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{calc}
\usetikzlibrary{bending} % Bend the arrow
\begin{document}
\begin{tikzpicture}[>={Stealth[length=0.3cm,bend]},
decoration={markings,
mark= at position .1 with {\arrow{>}},
mark= at position .32 with {\arrow{>}},
mark= at position .55 with {\arrow{>}},
mark= at position 0.88 with {\arrow{>}}, % <----
}
]
\def\gap{0.3}
\def\bigradius{3.4}
\def\littleradius{0.5}
\filldraw[postaction = {decorate}, thick ,fill=gray!40]
let
\n1 = {asin(\gap/2/\bigradius)},
\n2 = {asin(\gap/2/\littleradius)}
in
(0+\n1:\bigradius) node[above right]{$R$} arc (0+\n1:360-\n1:\bigradius) node[below left]{$C_{R}$} -- (0-\n2:\littleradius) arc (360-\n2:0+\n2:\littleradius) node[above right]{$\delta$} -- cycle;
\fill (-1.2,0) circle (3pt) ;
\draw[->] (-1.2,-1) node[right]{pole} --(-1.2,-0.15);
% axis
\draw[-Latex] (-1.5*\bigradius,0) -- (1.5*\bigradius,0) node[below]{$\Re$} ;
\draw[-Latex] (0,-1.2*\bigradius) -- (0,1.2*\bigradius) node[right]{$\Im$};
\end{tikzpicture}
\end{document}
如您所见，轮廓上的第四个箭头看起来很奇怪。我希望它沿着曲线弯曲，这就是我想要使用的原因\usetikzlibrary{bending}。
但在 中decoration，似乎箭头无法弯曲，bend命令无法生效。
我想问一下有什么解决办法吗？
我的一个解决方案：
\documentclass{standalone}
\usepackage{tikz}
\usepackage{physics}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{calc}
\usetikzlibrary{bending}% Bend the arrow
\begin{document}
\begin{tikzpicture}[>={Stealth[length=0.3cm,bend]},
decoration={markings,
mark= at position .1 with {\arrow{>}},
mark= at position .32 with {\arrow{>}},
mark= at position .55 with {\arrow{>}},
% mark= at position 0.88 with {\arrow{>}},
}
]
\def\gap{0.3}
\def\bigradius{3.4}
\def\littleradius{0.5}
\filldraw[postaction = {decorate}, thick ,fill=gray!40]
let
\n1 = {asin(\gap/2/\bigradius)},
\n2 = {asin(\gap/2/\littleradius)}
in
(0+\n1:\bigradius) node[above right]{$R$} arc (0+\n1:360-\n1:\bigradius) node[below left]{$C_{R}$} -- (0-\n2:\littleradius) arc (360-\n2:0+\n2:\littleradius) node[above right]{$\delta$} -- cycle;
% draw an arrow alone
\draw[thick,->] (300:\littleradius) arc (300:130:\littleradius) node[above]{$C_{\delta}$};
\fill (-1.2,0) circle (3pt) ;
\draw[->] (-1.2,-1) node[right]{pole} --(-1.2,-0.15);
% axis
\draw[-Latex] (-1.5*\bigradius,0) -- (1.5*\bigradius,0) node[below]{$\Re$} ;
\draw[-Latex] (0,-1.2*\bigradius) -- (0,1.2*\bigradius) node[right]{$\Im$};
\end{tikzpicture}
\end{document}
答案1
该hobby库允许通过给定的一组点绘制一条平滑的曲线。使用该markings库，可以记录装饰路径上的多个点，然后通过这些点绘制弯曲的箭头。这就是bent arrow at下面的样式所做的。在其当前形式中，它对曲线长度与示例中箭头长度相匹配的点的距离进行硬编码。
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{calc}
\usetikzlibrary{bending} % Bend the arrow
\usetikzlibrary{hobby}% smooth curve through a set of given points
\begin{document}
\begin{tikzpicture}[>={Stealth[length=0.3cm,bend]},
bent arrow at/.style={decoration={markings,
mark=at position {#1*\pgfdecoratedpathlength-0.15cm} with {\coordinate (bent arrow 1);},
mark=at position {#1*\pgfdecoratedpathlength-0.05cm} with {\coordinate (bent arrow 2);},
mark=at position {#1*\pgfdecoratedpathlength+0.05cm} with {\coordinate (bent arrow 3);},
mark=at position {#1*\pgfdecoratedpathlength+0.15cm} with {\coordinate (bent arrow 4);
\draw[-{Stealth[length=0.3cm,bend]}] (bent arrow 1) to[curve through={(bent arrow 2) .. (bent arrow 3)}] (bent arrow 4) ;}
}}
]
\def\gap{0.3}
\def\bigradius{3.4}
\def\littleradius{0.5}
\filldraw[postaction = {bent arrow at/.list={.1,.32,.55,.88},decorate}, thick ,fill=gray!40]
let
\n1 = {asin(\gap/2/\bigradius)},
\n2 = {asin(\gap/2/\littleradius)}
in
(0+\n1:\bigradius) node[above right]{$R$} arc (0+\n1:360-\n1:\bigradius) node[below left]{$C_{R}$} -- (0-\n2:\littleradius) arc (360-\n2:0+\n2:\littleradius) node[above right]{$\delta$} -- cycle;
\fill (-1.2,0) circle (3pt) ;
\draw[->] (-1.2,-1) node[right]{pole} --(-1.2,-0.15);
% axis
\draw[-Latex] (-1.5*\bigradius,0) -- (1.5*\bigradius,0) node[below]{$\Re$} ;
\draw[-Latex] (0,-1.2*\bigradius) -- (0,1.2*\bigradius) node[right]{$\Im$};
\end{tikzpicture}
\end{document}
答案2
仅供比较，以下是元帖子。MP 中的默认箭头始终遵循路径的曲线。这在内圈上更为明显。
这是包裹在luamplib所以您需要用 来编译它lualatex。
\documentclass[border=5mm]{standalone}
\usepackage{luamplib}
\begin{document}
\mplibtextextlabel{enable}
\begin{mplibcode}
beginfig(1);
% some control values
numeric delta, R, gap;
delta = 13; R = 89; gap = 3;
% axes and the region to fill
path re, im, region, little_ring, big_ring;
re = (left -- right) scaled 5/4 R;
im = re rotated 90;
little_ring = reverse fullcircle scaled 2 delta
cutbefore subpath (1/2, 1) of re shifted (0, -gap)
cutafter subpath (1/2, 1) of re shifted (0, +gap);
big_ring = fullcircle scaled 2 R
cutbefore subpath (1/2, 1) of re shifted (0, +gap)
cutafter subpath (1/2, 1) of re shifted (0, -gap);
region = little_ring -- big_ring -- cycle;
% do the filling first so it is on the bottom
% grey scale is just a single number between 0 and 1
fill region withcolor 7/8;
% use narrower arrowheads
ahangle := 36;
% draw the axes and the pole marker, with fine pen
drawoptions(withpen pencircle scaled 1/4);
drawarrow re;
drawarrow im;
z1 = (-3 delta, 0); z2 = z1 shifted 16 down;
draw z1 withpen pencircle scaled dotlabeldiam;
drawarrow z2 -- z1 cutafter fullcircle scaled 6 shifted z1;
drawoptions();
% bigger arrowheads for the integral path
ahlength := 6;
drawarrow subpath (0, 5) of region;
drawarrow subpath (5, 10) of region;
drawarrow subpath (10, 12.5) of region;
drawarrow subpath (12.5, 15.5) of region;
draw subpath (15.5, 18) of region;
% add the labels
label.bot("Pole", z2);
label.rt("$\Re$", point 1 of re);
label.top("$\Im$", point 1 of im);
label.urt("$\delta$", point 8 of little_ring);
label.urt("$R$", point 0 of big_ring);
label.ulft("$C_\delta$", point 5.3 of little_ring);
label.ulft("$C_R$", point 7.6 of big_ring);
endfig;
\end{mplibcode}
\end{document}