下一个代码
\PassOptionsToPackage{svgnames, x11names}{xcolor}
\documentclass[border=1cm, svgnames, x11names,tikz=true]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\begin{document}
\begin{tikzpicture}
\begin{axis}[width=4cm,height=4cm, scale only axis, axis x line=middle,axis y line=middle, axis on top,
xmin=-1.5,xmax=1.5,xtick=\empty,xticklabels=\empty, xlabel={$\ell_{1}$},
ymin=-1.5,ymax=1.5,ytick=\empty,yticklabels=\empty, ylabel={$\ell_{2}$},disabledatascaling]
\fill[color = green, opacity=0.1] (0:1.25) -- (0,0) -- (30:1.25) -- cycle;
\fill[color = green, opacity=0.2] (30:1.25) -- (0,0) -- (60:1.25) -- cycle;
\fill[color = green, opacity=0.3] (60:1.25) -- (0,0) -- (90:1.25) -- cycle;
\fill[color = green, opacity=0.4] (90:1.25) -- (0,0) -- (120:1.25) -- cycle;
\fill[color = green, opacity=0.5] (120:1.25) -- (0,0) -- (150:1.25) -- cycle;
\fill[color = green, opacity=0.6] (150:1.25) -- (0,0) -- (180:1.25) -- cycle;
\fill[color = green, opacity=0.7] (180:1.25) -- (0,0) -- (210:1.25) -- cycle;
\fill[color = green, opacity=0.8] (210:1.25) -- (0,0) -- (240:1.25) -- cycle;
\fill[color = green, opacity=0.9] (240:1.25) -- (0,0) -- (270:1.25) -- cycle;
\fill[color = green, opacity=1] (270:1.25) -- (0,0) -- (300:1.25) -- cycle;
\fill[color = green, opacity=1.1] (300:1.25) -- (0,0) -- (330:1.25) -- cycle;
\fill[color = green, opacity=1.2] (330:1.25) -- (0,0) -- (360:1.25) -- cycle;
\end{axis}
\end{tikzpicture}
\end{document}
生成下图：
有人知道原因吗？如果我用 Adobe Acrobat Pro 打开，图是：
