如何比较长宽比？

Question

我有一个盒子，其边长记录为

\newlength{\imageWidth} \setlength{\imageWidth}{300mm}
\newlength{\imageHeight} \setlength{\imageHeight}{200mm}

我正在尝试创建一个命令，该命令以图片的文件名作为参数，并将图片放置在框内，以保留纵横比并完全填充框（如果图像的纵横比宽于框的纵横比，则应剪切左侧、右侧和侧面）。

为此，我首先需要比较长宽比。我正在尝试的是

\settowidth{\imageFileWidth}{\includegraphics{#1}}
\settoheight{\imageFileHeight}{\includegraphics{#1}}

\ifnum\ratio{\imageFileWidth}{\imageFileHeight}>\ratio{\imageWidth}{\calHeight}
    \includegraphics[height=\imageHeight]{#1}
\else
    \includegraphics[width=\imageWidth]{#1}
\fi

使用该calc包。但是它不起作用，我不断收到Illegal unit of measure (pt inserted)错误Missing = inserted for \ifnum。

有什么建议吗？

更新感谢出色的回答解决了贝尔特我现在正在使用此代码进行简约的照片日历类光度计

Answer 1

如果比率较小，则可以使用\fpeval来生成 0，如果比率较大，则使用 1。我在 的分支中添加了一些额外的描述信息，您可以根据实际使用情况将其删除。我还\ifnum减少了 ，因此图像不会超出页面，至少在文章类的尺寸范围内不会超出页面。\imageWidth\imageHeight

\documentclass{article} 

\usepackage{graphicx}

\newlength{\imageWidth}
\setlength{\imageWidth}{60mm}
\newlength{\imageHeight}
\setlength{\imageHeight}{40mm}
\newlength{\imageFileWidth}
\newlength{\imageFileHeight}

\newcommand{\custompic}[1]{%
  \settowidth{\imageFileWidth}{\includegraphics{#1}}%
  \settoheight{\imageFileHeight}{\includegraphics{#1}}%
  \ifnum\fpeval{\the\imageFileWidth/\the\imageFileHeight > \the\imageWidth/\the\imageHeight}=1
    Greater:
    \fpeval{ceil(\the\imageFileWidth/\the\imageFileHeight,2)}%
    \textgreater
    \fpeval{ceil(\the\imageWidth/\the\imageHeight,2)}\par
    \includegraphics[height=\imageHeight]{#1}%
  \else
    Less:
    \fpeval{ceil(\the\imageFileWidth/\the\imageFileHeight,2)}%
    \textless
    \fpeval{ceil(\the\imageWidth/\the\imageHeight,2)}\par
    \includegraphics[width=\imageWidth]{#1}%
  \fi
  }

\begin{document}

\custompic{example-image-duck}

\custompic{example-image-4x3}

\end{document}

只是为了好玩，这是一个 expl3 实现。欢迎提出改进建议。

\documentclass{article} 

\usepackage{graphicx}

\ExplSyntaxOn
\dim_const:Nn \c_julian_width_dim { 60mm }
\dim_const:Nn \c_julian_height_dim { 40mm }
\fp_new:N \l_julian_fixedratio_fp
\fp_set:Nn \l_julian_fixedratio_fp
  {
    \dim_ratio:nn { \c_julian_width_dim } { \c_julian_height_dim }
  }
\fp_new:N \l_julian_tmpratio_fp
\box_new:N \l_julian_image_box
\cs_new:Nn \julian_custom_pic:n
  {
    \hbox_set:Nn \l_julian_image_box { \includegraphics{#1} }
    \fp_set:Nn \l_julian_tmpratio_fp
      {
        \dim_ratio:nn { \box_wd:N \l_julian_image_box } { \box_ht:N \l_julian_image_box }
      }
    \fp_compare:nNnTF { \l_julian_tmpratio_fp } > { \l_julian_fixedratio_fp }
      {
        Greater:~
        \fp_eval:n { ceil( \l_julian_tmpratio_fp, 2 ) }
        \textgreater
        \fp_eval:n { ceil( \l_julian_fixedratio_fp, 2 ) }\par
        \includegraphics[height=\c_julian_height_dim]{#1}%
      }
      {
        Less:~
        \fp_eval:n { ceil( \l_julian_tmpratio_fp, 2 ) }
        \textless
        \fp_eval:n { ceil( \l_julian_fixedratio_fp, 2 ) }\par
        \includegraphics[width=\c_julian_width_dim]{#1}%
      }
  }
\NewDocumentCommand { \custompic } { m } { \julian_custom_pic:n { #1 } }
\ExplSyntaxOff

\begin{document}

\custompic{example-image-duck}

\custompic{example-image-4x3}

\end{document}

再次为了好玩，这里有一个显示剪辑区域的版本。

\documentclass{article} 

\usepackage{graphicx,xcolor}

\ExplSyntaxOn
\dim_const:Nn \c_julian_width_dim { 60mm }
\dim_const:Nn \c_julian_height_dim { 40mm }
\fp_new:N \l_julian_fixedratio_fp
\fp_set:Nn \l_julian_fixedratio_fp
  {
    \dim_ratio:nn { \c_julian_width_dim } { \c_julian_height_dim }
  }
\fp_new:N \l_julian_tmpratio_fp
\box_new:N \l_julian_image_box
\cs_new:Nn \julian_custom_pic:n
  {
    \hbox_set:Nn \l_julian_image_box { \includegraphics{#1} }
    \fp_set:Nn \l_julian_tmpratio_fp
      {
        \dim_ratio:nn { \box_wd:N \l_julian_image_box } { \box_ht:N \l_julian_image_box }
      }
    \fp_compare:nNnTF { \l_julian_tmpratio_fp } > { \l_julian_fixedratio_fp }
      {
        \includegraphics[height=\c_julian_height_dim]{#1}%
      }
      {
        \includegraphics[width=\c_julian_width_dim]{#1}%
      }
  }
\NewDocumentCommand { \custompic } { m } { \julian_custom_pic:n { #1 } }
\ExplSyntaxOff

\setlength{\unitlength}{1mm}
\linethickness{1pt}

\newcommand{\showclip}[1]{%
  \begin{picture}(60,40)
  \color{red}
  \put(0,0){#1}
  \put(0,0){\line(0,1){40}}
  \put(60,0){\line(0,1){40}}
  \put(0,0){\line(1,0){60}}
  \put(0,40){\line(1,0){60}}
  \end{picture}
}

\begin{document}

\showclip{\custompic{example-image-duck}}

\vspace{1cm}

\showclip{\custompic{example-image-4x3}}

\end{document}