我使用的是texlive2020,texstudio,在编辑eps文件时出现了以下情况：
图(a),(b),(c)为jpg格式，可以看出其比较模糊，图（d）为eps格式，但只显示了标题 : 代码如下
\documentclass[CJK,a4paper,openany,10pt,oneside]{ctexart}
\usepackage{graphicx}
\usepackage{epstopdf}
\lineskip 0.5ex
\parskip 0.5ex
\makeatletter
\makeatother
\usepackage{amsmath, amsthm, amsfonts, amssymb}
\usepackage{mathrsfs}
\textwidth=15cm \textheight=22truecm \oddsidemargin 0.5cm
\evensidemargin 0.5cm
\usepackage{geometry}
\geometry{top=2.5cm}
\usepackage{algorithm,float}
\usepackage{algorithmic}
\usepackage{wrapfig}
\usepackage{fancyhdr}
\usepackage{mathtools}
\usepackage{xcolor,color}
\usepackage{esint}
\usepackage{enumerate}
\usepackage{bbm}
\numberwithin{equation}{section}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{definition}{Def}[section]
\newtheorem{corollary}[theorem]{Corollary}
\newtheorem{proposition}[theorem]{Proposition}
\newtheorem{lemma}[theorem]{Lemma}
\usepackage{mathrsfs}
\usepackage{appendix}
\usepackage[colorlinks,linkcolor=blue]{hyperref}
\usepackage{subcaption}
\newenvironment{breakablealgorithm}
{% \begin{breakablealgorithm}
\begin{center}
\refstepcounter{algorithm}% New algorithm
\hrule height.8pt depth0pt \kern2pt% \@fs@pre for \@fs@ruled
\renewcommand{\caption}[2][\relax]{% Make a new \caption
{\raggedright\textbf{\ALG@name~\thealgorithm} ##2\par}%
\ifx\relax##1\relax % #1 is \relax
\addcontentsline{loa}{algorithm}{\protect\numberline{\thealgorithm}##2}%
\else % #1 is not \relax
\addcontentsline{loa}{algorithm}{\protect\numberline{\thealgorithm}##1}%
\fi
\kern2pt\hrule\kern2pt
}
}{% \end{breakablealgorithm}
\kern2pt\hrule\relax% \@fs@post for \@fs@ruled
\end{center}
}
\begin{document}
\begin{figure}[ht]
\centering
\begin{minipage}{4cm}
\includegraphics[width=4cm]{N=5.png}
\subcaption{N=5}
\end{minipage}
\begin{minipage}{4cm}
\includegraphics[width=4cm]{N=10}
\subcaption{N=10}
\end{minipage}
\begin{minipage}{4cm}
\includegraphics[width=4cm]{N=20}
\subcaption{k=20}
\end{minipage}
\begin{minipage}{4cm}
\includegraphics[width=4cm]{N=40.eps}
\subcaption{N=40}
\end{minipage}
\caption{数值解与精确解}
\end{figure}
\end{document}请问是哪里出了问题呢？（附件中为所用到的图片）
