关于此代码，我对箭头的颜色有疑问：我想制作两个箭头，其中第一个箭头以蓝色开始，以红色结束。为什么如果我编写此代码，LaTeX 会为箭头下方的空间着色？
代码
\PassOptionsToPackage{svgnames, x11names}{xcolor}
\documentclass{article}
\usepackage[a4paper,top=3cm,bottom=3cm,left=1.5cm,right=1.5cm]{geometry}
\usepackage[T1]{fontenc}
\usepackage{amssymb}
\usepackage{extarrows}
\usepackage{stix}
\usepackage{tikz}
%\usetikzlibrary{decorations.markings}
\usepackage[bb=ams]{mathalpha}
\newcommand{\Tonde}[1]{\left(#1\right)}
\newcommand{\tonde}[1]{\bigl(#1\bigr)}
\begin{document}
\begin{center}
\begin{tikzpicture}
\draw[thick, dashed, -latex, shorten >= 3pt, left color = blue, right color = red]
(-2, 3.5)
to[out=15, in=155] node[above, font=\Large]{$f$}
( 2.5, 3.25);
\draw[thick, dashed, -latex, shorten >= 3pt, left color = green, right color = Silver]
(-1.25,2.75)
to[out=15, in=155] node[above, font=\Large]{$\bar f$} node[below, font=\Large]{$\eqqsim$}
( 3.00,2.25);
\end{tikzpicture}
\end{center}
\end{document}
第一次编辑：我将以前的代码编辑成
\PassOptionsToPackage{svgnames, x11names}{xcolor}
\documentclass[a4paper]{article}
\usepackage{stix}
\usepackage{tikz}
\usetikzlibrary{fadings,decorations.pathmorphing}
\makeatletter
\newif\iftikz@shading@path
\tikzset{
% Need this for the bounding box calculation of the
% fading and the rectangle that bounds the fading.
% If set to zero things (e.g., arrows) may get cut off.
fading sep/.store in=\fadingsep,
fading sep=0.25cm,
shaded path/.code={%
% Prevent this stuff happning recursively.
\iftikz@shading@path%
\else%
\tikz@shading@pathtrue%
\tikz@addmode{%
% Interrupt the picture to create a fading.
\pgfinterruptpicture%
\begin{tikzfadingfrompicture}[name=.]
\path [shade=none,fill=none]#1;%
% Need to set the bounding box manually. Include the \fadingsep border.
\xdef\fadingboundingbox{{\noexpand\pgfpoint{\the\pgf@picminx-\fadingsep}{\the\pgf@picminy-\fadingsep}}%
{\noexpand\pgfpoint{\the\pgf@picmaxx+\fadingsep}{\the\pgf@picmaxy+\fadingsep}}}%
\expandafter\pgfpathrectanglecorners\fadingboundingbox%
\pgfusepath{discard}%
\end{tikzfadingfrompicture}%
\endpgfinterruptpicture%
% Install a rectangle that covers the shaded/faded path.
\expandafter\pgfpathrectanglecorners\fadingboundingbox%
% Make the fading happen.
\def\tikz@path@fading{.}%
\tikz@mode@fade@pathtrue%
\tikz@fade@adjustfalse%
\pgfpointscale{0.5}{\expandafter\pgfpointadd\fadingboundingbox}%
\def\tikz@fade@transform{shift={(\the\pgf@x,\the\pgf@y)}}%
}%
\fi%
}
}
\begin{document}
\begin{tikzpicture}[line cap=round, line join=round]
\path[font=\Huge]
(-5.5, 2.5) node[blue] {$U$}
( 7.25, 2.5) node[red] {$V$}
(-3.5, 2.5) node[green] {$U'$}
( 5.75, 2.5) node[Silver] {$V'$};
\path[save path=\pathU]
(-6, 0.5) to[out= 80, in=310, looseness=1] (-4.5, 3)
to[out=140, in=160, looseness=1] (-3, 4)
to[out=-30, in=160] (-1, 3)
to[out=-20, in=100] ( 0, 2)
to[out=-90, in= 15, looseness=1] (-1, 0.5)
to[out=190, in=-10] (-2, 0.75)
to[out=170, in= 10, looseness=1.5] (-5, 0)
to[out=190, in=270, looseness=1.5] (-6, 0.5);
\begin{scope}
\clip[use path=\pathU];
\draw[very thin, dashed, cyan, step=0.5] (-6, 0) grid (0, 4);
\end{scope}
\draw[thick, blue, use path=\pathU];
\path[save path=\pathV]
(2.25, 1) to[out= 90, in=180, looseness=1.8] (4.50, 3.50)
to[out= 45, in= 90, looseness=1.25] (6.50, 2.25)
to[out=-90, in=-20, looseness=1.75] (4.50, 0.50)
to[out=170, in=-75, looseness=1] (2.25, 1 );
\begin{scope}
\clip[use path=\pathV];
\draw[very thin, dashed, orange]
\foreach\x in{2, 2.5, ..., 6}
{
(\x, 4) to (\x, 3.5)
to (\x, 3.25)
to (\x, 2.25)
to (\x, 1.25)
to (\x, 0.75)
to (\x, 0.25)
}
\foreach\y in{3.25, 2.75, ..., 0.25}
{(2, \y) to (6.5, \y)};
\end{scope}
\draw[thick, red, use path=\pathV];
\path [left color=red, right color=blue, shaded path={
[draw=transparent!0, ultra thick, -stealth] (-2, 3.5)
to[out=15, in=155] node[above, font=\Large]{$f$}
( 2.5, 3.25);
}];
\path [left color=green, right color=Silver, shaded path={
[draw=transparent!0, ultra thick, -stealth]
(-1.25,2.75)
to[out=15, in=155] node[above, font=\Large]{$\bar f$} node[below, font=\Large]{$\eqqsim$}
( 3.00,2.25);
}];
\draw[thick, dashed, -latex, shorten >= 3pt, color = Goldenrod] (4,2.25) to[out=240, in=-60] node[below, font=\Large]{$g=f^{-1}$} (-2,2);
\begin{scope}[thick]
\draw[color = green] (-2,2.00) circle (1cm);
\draw[color = Silver] ( 4,2.25) circle (1cm);
\draw[color = green] (-2,2) circle (1.5pt) node[above]{$u$};
\draw[color = Silver] (4,2.25) circle (1.5pt) node[above]{$v$};
\end{scope}
\end{tikzpicture}
\end{document}
第二次编辑：编译新代码，我得到了一个不想要的结果：我想要的是创建我之前描述的两个箭头。
第三次编辑：我修正了我的代码，但没有箭头。此外，节点上出现了彩色方块（为什么？）。有人可以修正我的代码吗？
太感谢了
答案1
最后我自己找到了解决方案，现在发布在这里
\PassOptionsToPackage{svgnames, x11names}{xcolor}
\documentclass[a4paper]{article}
\usepackage{stix}
\usepackage{tikz}
\usetikzlibrary{fadings,decorations.pathmorphing}
\makeatletter
\newif\iftikz@shading@path
\tikzset{
% Need this for the bounding box calculation of the
% fading and the rectangle that bounds the fading.
% If set to zero things (e.g., arrows) may get cut off.
fading sep/.store in=\fadingsep,
fading sep=0.25cm,
shaded path/.code={%
% Prevent this stuff happning recursively.
\iftikz@shading@path%
\else%
\tikz@shading@pathtrue%
\tikz@addmode{%
% Interrupt the picture to create a fading.
\pgfinterruptpicture%
\begin{tikzfadingfrompicture}[name=.]
\path [shade=none,fill=none]#1;%
% Need to set the bounding box manually. Include the \fadingsep border.
\xdef\fadingboundingbox{{\noexpand\pgfpoint{\the\pgf@picminx-\fadingsep}{\the\pgf@picminy-\fadingsep}}%
{\noexpand\pgfpoint{\the\pgf@picmaxx+\fadingsep}{\the\pgf@picmaxy+\fadingsep}}}%
\expandafter\pgfpathrectanglecorners\fadingboundingbox%
\pgfusepath{discard}%
\end{tikzfadingfrompicture}%
\endpgfinterruptpicture%
% Install a rectangle that covers the shaded/faded path.
\expandafter\pgfpathrectanglecorners\fadingboundingbox%
% Make the fading happen.
\def\tikz@path@fading{.}%
\tikz@mode@fade@pathtrue%
\tikz@fade@adjustfalse%
\pgfpointscale{0.5}{\expandafter\pgfpointadd\fadingboundingbox}%
\def\tikz@fade@transform{shift={(\the\pgf@x,\the\pgf@y)}}%
}%
\fi%
}
}
\begin{document}
\Large
\begin{tikzpicture}[line cap=round, line join=round]
\path[font=\Huge]
(-5.5, 2.5) node[blue] {$U$}
( 7.25, 2.5) node[red] {$V$}
(-3.5, 2.5) node[green] {$U'$}
( 5.75, 2.5) node[Silver] {$V'$};
\path[save path=\pathU]
(-6, 0.5) to[out= 80, in=310, looseness=1] (-4.5, 3)
to[out=140, in=160, looseness=1] (-3, 4)
to[out=-30, in=160] (-1, 3)
to[out=-20, in=100] ( 0, 2)
to[out=-90, in= 15, looseness=1] (-1, 0.5)
to[out=190, in=-10] (-2, 0.75)
to[out=170, in= 10, looseness=1.5] (-5, 0)
to[out=190, in=270, looseness=1.5] (-6, 0.5);
\begin{scope}
\clip[use path=\pathU];
\draw[very thin, dashed, cyan, step=0.5] (-6, 0) grid (0, 4);
\end{scope}
\draw[thick, blue, use path=\pathU];
\path[save path=\pathV]
(2.25, 1) to[out= 90, in=180, looseness=1.8] (4.50, 3.50)
to[out= 45, in= 90, looseness=1.25] (6.50, 2.25)
to[out=-90, in=-20, looseness=1.75] (4.50, 0.50)
to[out=170, in=-75, looseness=1] (2.25, 1 );
\begin{scope}
\clip[use path=\pathV];
\draw[very thin, dashed, orange]
\foreach\x in{2, 2.5, ..., 6}
{
(\x, 4) to (\x, 3.5)
to (\x, 3.25)
to (\x, 2.25)
to (\x, 1.25)
to (\x, 0.75)
to (\x, 0.25)
}
\foreach\y in{3.25, 2.75, ..., 0.25}
{(2, \y) to (6.5, \y)};
\end{scope}
\draw[thick, red, use path=\pathV];
\path [left color=blue, right color=red, shaded path={
[draw=transparent!0, dashed, thick, -stealth]
(-2, 3.5) to[out=15, in=155] ( 2.5, 3.25);
}];
\path [left color=green, right color=Silver, shaded path={
[draw=transparent!0, thick, dashed, -stealth, -latex, shorten >= 3pt] (-1.25,2.75) to[out=15, in=155] ( 3.00,2.25);
}];
\draw[thick, dashed, -latex, shorten >= 3pt, color = Goldenrod] (4,2.25) to[out=240, in=-60] node[below, font=\Large]{$g=f^{-1}$} (-2,2);
\begin{scope}[thick]
\draw[color = green] (-2,2.00) circle (1cm);
\draw[color = Silver] ( 4,2.25) circle (1cm);
\draw[color = green] (-2,2) circle (1.5pt) node[above]{$u$};
\draw[color = Silver] (4,2.25) circle (1.5pt) node[above]{$v$};
\end{scope}
\begin{scope}
\node at (0.25, 4.25) {$f$};
\node at (0.75, 3.25) {$\bar f$};
\node at (0.75, 2.50) {$\eqqsim$};
\end{scope}
\end{tikzpicture}
\end{document}
事实上，得到的输出正是我想要的，即
