PDF 和 PNG 大小不同

Question

当我使用不同类型的图片（png 和 pdf）时，尽管用相同的尺寸定义它们，但我得到的尺寸却不同，如下所示。下面是我使用的包和代码：

\begin{figure}
        \hfill
        \subfigure[J8]{\includegraphics[width=7.5cm]{Figure32Graph28c.png}}
        \hfill
        \subfigure[CT]{\includegraphics[width=7.5cm]{Figure32Graph28d.png}}
        \hfill
        \subfigure[J]{\includegraphics[width=7.5cm]{Figure32Graph28f.pdf}}
        \hfill
        \subfigure[CT]{\includegraphics[width=7.5cm]{Figure32Graph28e.pdf}}
        \hfill
        \caption{Accuracy Results }
        \label{fig:DS3}
    \end{figure}

以下是包裹等：

\begin{filecontents*}{example.eps}
    %!PS-Adobe-3.0 EPSF-3.0
    %%BoundingBox: 19 19 221 221
    %%CreationDate: Mon Sep 29 1997
    %%Creator: programmed by hand (JK)
    %%EndComments
    gsave
    newpath
    20 20 moveto
    20 220 lineto
    220 220 lineto
    220 20 lineto
    closepath
    2 setlinewidth
    gsave
    .4 setgray fill
    grestore
    stroke
    grestore
\end{filecontents*}
%
\RequirePackage{fix-cm}
%
%\documentclass{svjour3}                     % onecolumn (standard format)
%\documentclass[smallcondensed]{svjour3}     % onecolumn (ditto)
\documentclass[smallextended]{svjour3}       % onecolumn (second format)
%\documentclass[twocolumn]{svjour3}          % twocolumn
%\smartqed  % flush right qed marks, e.g. at end of proof
%
%\usepackage{graphicx}
%
% \usepackage{mathptmx}      % use Times fonts if available on your TeX system
%
% insert here the call for the packages your document requires
%\usepackage{latexsym}
% etc.
%

% \documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{graphicx}
\usepackage{algpseudocode}
\usepackage{algorithm}
\usepackage{authblk}
\usepackage{textcomp}
\usepackage{mathtools}
\usepackage{filecontents}
\usepackage{microtype}
\usepackage{float}
\usepackage{adjustbox}
\usepackage{booktabs,makecell,tabularx}
\usepackage{url}
\usepackage{booktabs}
\usepackage{subfigure}

\newcommand{\tvar}[2]{%
    \mathrm{#1}_{\mathrm{#2}}%
}
\renewcommand\theadfont{\small}
\newcolumntype{C}[1]{>{\centering\arraybackslash}p{#1}}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\usepackage{siunitx}

%\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{siunitx}
\usepackage{etoolbox}
\usepackage{tabularx, booktabs, makecell} %

%\\usepackage[symbol*]{footmisc}
%\usepackage[round]{natbib} 
\usepackage[square,numbers]{natbib} 
\renewcommand{\thetable}{\arabic{table}}

%\usepackage{siunitx,etoolbox}
%\renewrobustcmd{\bfseries}{\fontseries{b}\selectfont}
%\renewrobustcmd{\boldmath}{}
%\newrobustcmd{\B}{\bfseries}

\usepackage{lmodern}
\usepackage{siunitx}
\usepackage{booktabs}
\usepackage{etoolbox}


% please place your own definitions here and don't use \def but
% \newcommand{}{}
%
% Insert the name of "your journal" with
% \journalname{myjournal}
%

\usepackage[a4paper,margin=1in,footskip=0.25in]{geometry}
\begin{document}
   ... // insert the above code here!!!!
\end{document}

结果如下\fbox：

\fbox{\includegraphics[width=7.5cm]{Figure32Graph28e.pdf}}