Is it possible to store the height and width of an imported document in variables and adjust the page to fit it (reverse-engineering layouts)?

Question

For example, let's say that I use the pdfpages package and import a PDF. Is there any way (without using an external scripting language like Python) to access the dimensions of the PDF? Can I pass those dimensions to the geometry package?

I would like a simple way to create a document output that

• fits page geometry to an inputted file precisely
• draws a grid over the entire document (see How can I make a perfect page grid that fits my page for measuring purposes in TikZ?)

The grid overlay should be drawn efficiently using these new dimensions (variables grabbed from input should be passed to TikZ), because I don't want to just make the grid big enough to cover any likely paper size (not very efficient for inputs with smaller dimensions).

Purpose

This is useful for reverse-engineering PDF templates/layouts (e.g. from InDesign) or images. By reverse-engineering, I mean that I can easily design precise layouts with TikZ's page coordinates.

Code

In this example, I commented out a pdfinput in the body. I want to grab the pdf dimensions at that point and create \setpaperwidth and \setpaperheight macros that set the \inputwidth and \inputheight variables.

\documentclass{article}
\usepackage{fontspec}

\newcommand\inputwidth{5.5in}  % <- set from input
\newcommand\inputheight{8.5in} % <- set from input

\usepackage[%
paperwidth=\inputwidth,  
paperheight=\inputheight,  
verbose,             % show the values of the parameters in the log file
]{geometry}

\usepackage{pdfpages}
\usepackage{tikz} % Support for drawing grid
\usetikzlibrary{backgrounds,calc}
\usepackage{atbegshi} % Add support for the showgrid overlay
\newcommand{\showgrid}{%
  \AtBeginShipoutNext{\AtBeginShipoutAddToBoxForeground{%
      \begin{tikzpicture}
        [
          overlay,
          remember picture,
          inner sep=0pt,
          outer sep=0pt,
          minor line/.style={help lines, draw=black!50, on background layer},
          major line/.style={help lines, draw=black},
          major number/.style={font=\fontsize{3}{5}\selectfont\bfseries},
          minor number/.style={font=\fontsize{1}{2}\selectfont},
        ]
        \pgfmathtruncatemacro\xmaxstep{\paperwidth/1mm}% calculate needed steps in x direction
        \pgfmathtruncatemacro\ymaxstep{\paperheight/1mm}% calculate needed steps in y direction
        \foreach \step in {0,1,...,\xmaxstep} {
          \pgfmathsetmacro\gridlineconfig{ifthenelse(equal(int(mod(\step,10)),0),"major line","minor line")}%
          \draw [\gridlineconfig] ($(current page.north west) + (\step mm,0)$) -- ($(current page.south west) + (\step mm,0)$);
        }
        \foreach \step in {0,1,...,\ymaxstep} {
          \pgfmathsetmacro\gridlineconfig{ifthenelse(equal(int(mod(\step,10)),0),"major line","minor line")}%
          \pgfmathsetmacro\numberconfig{ifthenelse(equal(int(mod(\step,10)),0),"major number","minor number")}%
          \draw [\gridlineconfig] ($(current page.north west) - (0,\step mm)$) -- ($(current page.north east) - (0,\step mm)$);
          \node [anchor=north,\numberconfig] at ($ (current page.north west) + (\step mm,0) $) {\step};
          \node [anchor=west,\numberconfig] at ($ (current page.north west) - (0,\step mm) $) {\step};
        }
      \end{tikzpicture}
    }%
  }%
}
\pagenumbering{gobble} % Remove Page Numbers (without fancyhdr)
\begin{document}
\showgrid
\null
%\includepdf[noscale]{pdffile.pdf} % <- Grab dimensions here
\end{document}

Answer 1

You can use graphicx's \includegraphics to store a page of the document and measure it:

\newsavebox{\measurebox}
\newlength{\measuredwidth}
\newlength{\measuredheight}
\newcommand\measureimage[2][1]{%
    \savebox{\measurebox}{\includegraphics[page=#1]{#2}}%
    \setlength{\measuredwidth}{\wd\measurebox}%
    \setlength{\measuredheight}{\ht\measurebox}%
    \savebox{\measurebox}{}%
    }

...

\measureimage[2]{myfigure} % measures the 2nd page of the file.

\showthe\measuredwidth % shows the width
\showthe\measuredheight % shows the height

After issuing \measureimage[pagenumber]{filename}, the width and height of the image are stored in \measurewidth and \measuredheight. The default page number is 1. Just remember that doing this is not quite fast so you should use it only a small number of files (it wouldn't be good if you needed to measure each page separately).

Answer 2

Fit Page Dimensions to Input and Draw Grid Overlay

After experimenting with yo's answer, I found a way to achieve this with any PDF or image file input.

Given image hike.png:

• identify -format "%wx%h\n" hike.png -> 483x271
• file hike.png- > hike.png: PNG image data, 483 x 271, 8-bit/color RGBA, non-interlaced

Include in body with \measureimage[1]{hike.png}, which does the following:

1. Grab dimensions of hike.png
2. Reset paperwidth and paperheight for TikZ nodes
3. Reset pdfpaperwidth and pdfpaperheight for actual paper size output with \eject
4. Add image overlay using TikZ node
5. Apply grid over image (using \pdfpagewidth and \pdfpageheight for x and y max values) in 1 millimeter intervals.

Code

\documentclass{article}
\usepackage{fontspec}

\usepackage[%
%paperwidth=\inputwidth,  % Unneeded
%paperheight=\inputheight,% Unneeded
verbose,             % show the values of the parameters in the log file
]{geometry}

\usepackage{pdfpages}
\usepackage{tikz} % Support for drawing grid
\usetikzlibrary{backgrounds,calc}
\usepackage{atbegshi} % Add support for the showgrid overlay
\newcommand{\showgrid}{%
  \AtBeginShipoutNext{\AtBeginShipoutAddToBoxForeground{%
      \begin{tikzpicture}
        [
          overlay,
          remember picture,
          inner sep=0pt,
          outer sep=0pt,
          minor line/.style={help lines, draw=black!50, on background layer},
          major line/.style={help lines, draw=black},
          major number/.style={font=\fontsize{3}{5}\selectfont\bfseries},
          minor number/.style={font=\fontsize{1}{2}\selectfont},
        ]
        \pgfmathtruncatemacro\xmaxstep{\pdfpagewidth/1mm}% calculate needed steps in x direction
        \pgfmathtruncatemacro\ymaxstep{\pdfpageheight/1mm}% calculate needed steps in y direction
        \foreach \step in {0,1,...,\xmaxstep} {
          \pgfmathsetmacro\gridlineconfig{ifthenelse(equal(int(mod(\step,10)),0),"major line","minor line")}%
          \draw [\gridlineconfig] ($(current page.north west) + (\step mm,0)$) -- ($(current page.south west) + (\step mm,0)$);
        }
        \foreach \step in {0,1,...,\ymaxstep} {
          \pgfmathsetmacro\gridlineconfig{ifthenelse(equal(int(mod(\step,10)),0),"major line","minor line")}%
          \pgfmathsetmacro\numberconfig{ifthenelse(equal(int(mod(\step,10)),0),"major number","minor number")}%
          \draw [\gridlineconfig] ($(current page.north west) - (0,\step mm)$) -- ($(current page.north east) - (0,\step mm)$);
          \node [anchor=north,\numberconfig] at ($ (current page.north west) + (\step mm,0) $) {\step};
          \node [anchor=west,\numberconfig] at ($ (current page.north west) - (0,\step mm) $) {\step};
        }
      \end{tikzpicture}
    }%
  }%
}
\pagenumbering{gobble} % Remove Page Numbers (without fancyhdr)

\newsavebox{\measurebox}
\newlength{\measuredwidth}
\newlength{\measuredheight}

\newcommand\measureimage[2][1]{%
    \savebox{\measurebox}{\includegraphics[page=#1]{#2}}%
    \setlength{\measuredwidth}{\wd\measurebox}%
    \setlength{\measuredheight}{\ht\measurebox}%
    \savebox{\measurebox}{}%
    \paperwidth=\measuredwidth \paperheight=\measuredheight     % paper dimensions for TikZ page nodes
    \eject \pdfpagewidth=\measuredwidth \pdfpageheight=\measuredheight % set paper dimensions in XeLaTeX
    \tikz [overlay, remember picture] \node [anchor=north west,inner sep=0pt,outer sep=0pt] at (current page.north west) {\includegraphics[page=#1]{#2}};
    \showgrid
    }

\begin{document}
\measureimage[1]{hike.png} % measures the 2nd page of the file.

%Height: \the\measuredwidth % shows the width of the paper 

%Width: \the\measuredheight % shows the height of the paper
\end{document}

Output