如何在代码中为白色矩形添加如下图所示的阴影效果？

Question

\documentclass[12pt]{article}
\usepackage{tikz}
\usetikzlibrary{arrows, shapes, positioning}
\begin{document}
\pagestyle{empty}
\pagecolor{blue!50}
\begin{tikzpicture}[remember picture, overlay]
\fill[fill=white]([xshift=23mm, yshift=-23mm]current page.north west)rectangle([xshift=-23mm, yshift=-227mm]current page.north east);
\end{tikzpicture}
\end{document}

[

Answer 1

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shadows.blur}
\begin{document}
\pagestyle{empty}
\pagecolor{blue!50}
\begin{tikzpicture}[remember picture, overlay]
\fill[blur shadow={shadow xshift=5pt, shadow yshift=0pt, shadow blur radius=5pt},  white] ([xshift=23mm, yshift=-23mm]current page.north west)rectangle([xshift=-23mm, yshift=-227mm]current page.north east);
\end{tikzpicture}
\end{document}

编辑：

阴影不太明显：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shadows.blur}
\begin{document}
\pagestyle{empty}
\pagecolor{blue!20}
\begin{tikzpicture}[remember picture, overlay]
\fill[blur shadow={shadow xshift=5pt, shadow yshift=0pt, shadow blur radius=5pt, shadow opacity=20}, white,
] ([xshift=23mm, yshift=-23mm]current page.north west)rectangle([xshift=-23mm, yshift=-227mm]current page.north east);
\end{tikzpicture}
\end{document}

shadows.blur无法改变颜色，但您可以手动添加阴影，如下所示：

\documentclass{article}
\usepackage{tikz}
\begin{document}
\pagestyle{empty}
\pagecolor{blue!20}
\begin{tikzpicture}[remember picture, overlay]
\foreach \x in {0,0.025,...,1}
 \draw[blue!50, opacity=\x, thick] ([xshift=-23mm+10-10*\x, yshift=-23mm]current page.north east) -- ([xshift=-23mm+10-10*\x, yshift=-227mm]current page.north east);
\fill[white] ([xshift=23mm, yshift=-23mm]current page.north west)rectangle([xshift=-23mm, yshift=-227mm]current page.north east);
\end{tikzpicture}
\end{document}