twoimages.tex

\documentclass{article}
\usepackage{graphicx,calc,lipsum}

\makeatletter
\newcommand*{\DivideLengths}[2]{%
  \strip@pt\dimexpr\number\numexpr\number\dimexpr#1\relax*65536/\number\dimexpr#2\relax\relax sp\relax
}
\makeatother

\newsavebox\IBoxA \newsavebox\IBoxB \newlength\IHeight
\newlength\RatioA \newlength\RatioB \newlength\ScaleFactor
\newdimen\Width \newdimen\RatioSum \newdimen\RatioSumInverse \newdimen\TextWidth \newdimen\IWidthA \newdimen\IWidthB
\def\Padding{5pt}
\newcommand\TwoFig[6]{% Image1 Caption1 Label1 Im2 Cap2 Lab2
    \sbox\IBoxA{\includegraphics{#1}}\sbox\IBoxB{\includegraphics{#4}}%
    \ifdim\ht\IBoxA>\ht\IBoxB\setlength\IHeight{\ht\IBoxA}\else\setlength\IHeight{\ht\IBoxB}\fi
    \setlength\RatioA{\DivideLengths{\wd\IBoxA}{\ht\IBoxA}pt}
    \setlength\RatioB{\DivideLengths{\wd\IBoxB}{\ht\IBoxB}pt}
    \RatioSum=\dimexpr(\RatioA+\RatioB)
    \RatioSumInverse=\DivideLengths{1.0pt}{\RatioSum}pt
    \Width=\DivideLengths{\IHeight}{\RatioSumInverse}pt
    \TextWidth=\dimexpr(\textwidth-\Padding)
    \setlength\ScaleFactor{\DivideLengths{\TextWidth}{\Width}pt}%
    \IWidthA=\dimexpr(\DivideLengths{\RatioA}{\DivideLengths{1.0pt}{\DivideLengths{\ScaleFactor}{\DivideLengths{1.0pt}{\IHeight}pt}pt}pt}pt-1pt)
    \IWidthB=\dimexpr(\DivideLengths{\RatioB}{\DivideLengths{1.0pt}{\DivideLengths{\ScaleFactor}{\DivideLengths{1.0pt}{\IHeight}pt}pt}pt}pt-1pt)
    %
    \begin{figure}[!htb]\centering%
        \minipage[t]{\IWidthA}\centering%
        \frame{\includegraphics[width=\IWidthA]{#1}}%
        \caption{#2}\label{#3}%
        \endminipage\hspace{\Padding}%
        \minipage[t]{\IWidthB}\centering%
        \frame{\includegraphics[width=\IWidthB]{#4}}%
        \caption{#5}\label{#6}%
        \endminipage%
    \end{figure}%
    % Uncomment to see actual values:
    %     textwidth: \the\textwidth\\
    %     Width: \the\Width\\
    %     TextWidth: \the\TextWidth\\
    %     RatioSum: \the\RatioSum\\
    %     RatioSumInverse: \the\RatioSumInverse\\
    %     ScaleFactor: \the\ScaleFactor\\
    %     Width BoxA: \the\wd\IBoxA\\
    %     Height BoxA: \the\ht\IBoxA\\
    %     RatioA: \the\RatioA\\
    %     Width BoxB: \the\wd\IBoxB\\
    %     Height BoxB: \the\ht\IBoxA\\
    %     RatioB: \the\RatioB\\
    %     IHeight: \the\IHeight\\
    %     IWidthA: \the\IWidthA\\
    %     IWidthB: \the\IWidthB\\
}

\begin{document}

  \lipsum[1]

  \TwoFig{images/image1}{Image 2 Description}{fig:image1}%
      {images/image2}{Image 1 Description}{fig:image2}

  \lipsum[2]

\end{document}