# Exact Tikz coordinate at geometry layout

I place several images on one page using Tikz. I use geometry layout. I would like to find out exact coordinate of the left top corner of the layout page (not the real page). I have found out coordinate script, but I am not sure if it is necessary. Any suggestions are welcome. Note: The aim is to centre final Tikz picture (consisting of several images and labels) on the layout page.

\documentclass[12pt]{extbook}
% ############################## geometry
\usepackage%[showframe]
{geometry}
\geometry
{ hmarginratio =  1:1
, vmarginratio = 1:1
, bindingoffset = 0cm
, onecolumn
, a4paper
, layoutwidth = 50 mm
, layoutheight = 180 mm
, layouthoffset=\dimexpr(\paperwidth-\csname Gm@layoutwidth\endcsname)/2\relax
, layoutvoffset=\dimexpr(\paperheight-\csname Gm@layoutheight\endcsname)/2\relax
, showcrop
}
\usepackage{fancyhdr}
\usepackage{mwe}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{calc}

\makeatletter
\def\parsecomma#1,#2\endparsecomma{\def\page@x{#1}\def\page@y{#2}}
\tikzdeclarecoordinatesystem{page}{
\parsecomma#1\endparsecomma
\pgfpointanchor{current page}{north east}
% Save the upper right corner
\pgf@xc=\pgf@x%
\pgf@yc=\pgf@y%
% save the lower left corner
\pgfpointanchor{current page}{south west}
\pgf@xb=\pgf@x%
\pgf@yb=\pgf@y%
% Transform to the correct placement
\pgfmathparse{(\pgf@xc-\pgf@xb)/2.*\page@x+(\pgf@xc+\pgf@xb)/2.}
\expandafter\pgf@x\expandafter=\pgfmathresult pt
\pgfmathparse{(\pgf@yc-\pgf@yb)/2.*\page@y+(\pgf@yc+\pgf@yb)/2.}
\expandafter\pgf@y\expandafter=\pgfmathresult pt
}
\makeatother

% ############################### Document
\begin{document}
\thispagestyle{empty}
\begin{tikzpicture}[remember picture, overlay]
\node[inner sep=0pt] (A) at (page cs:0,0.5)
{\includegraphics[width=5cm]{example-image}};
\draw[black, thick] ($(A.north west)$)  rectangle ($(A.south east)$);
\node[inner sep=0pt] (B) at ([yshift=-71pt]A.south)
{\includegraphics[width=5cm]{example-image}};
\draw[black,thick] ($(B.north west)$)  rectangle ($(B.south east)$);
\end{tikzpicture}
\end{document}

• I am not sure if it is by chance, but in real document with more complicated tikzpicture, the picture is centered vertically and horizontally in layout page. – chejnik Feb 18 '16 at 14:36

Here is another way to locate the center of the layout area. (Whether or not it is simpler...)

\documentclass[12pt]{extbook}
% ############################## geometry
\usepackage%[showframe]
{geometry}

\makeatletter% rename layout variables
\def\layoutwidth{\Gm@layoutwidth}
\def\layoutheight{\Gm@layoutheight}
\def\layouthoffset{\Gm@layouthoffset}
\def\layoutvoffset{\Gm@layoutvoffset}
\makeatother

\geometry
{ hmarginratio =  1:1
, vmarginratio = 1:1
, bindingoffset = 0cm
, onecolumn
, a4paper
, layoutwidth = 50 mm
, layoutheight = 180 mm
, layouthoffset=\dimexpr(\paperwidth-\layoutwidth)/2\relax
, layoutvoffset=\dimexpr(\paperheight-\layoutheight)/2\relax
, showcrop
}

\usepackage{fancyhdr}
\usepackage{mwe}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{calc}

\newsavebox{\tempbox}

% ############################### Document
\begin{document}
\thispagestyle{empty}

\savebox{\tempbox}{%
\begin{tikzpicture}
\node[inner sep=0pt] (A) at (0,0.5)
{\includegraphics[width=5cm]{example-image}};
\draw[black, thick] ($(A.north west)$)  rectangle ($(A.south east)$);
\node[inner sep=0pt] (B) at ([yshift=-71pt]A.south)
{\includegraphics[width=5cm]{example-image}};
\draw[black,thick] ($(B.north west)$)  rectangle ($(B.south east)$);
\end{tikzpicture}}

\begin{tikzpicture}[remember picture, overlay]
\path (current page.north west) ++(\layouthoffset,-\layoutvoffset)
++(0.5\layoutwidth,-0.5\layoutheight) coordinate(Center);
\node[inner sep=0pt] at (Center) {\usebox{\tempbox}};
\end{tikzpicture}
\end{document}

• Please can you explain how it works? Many thanks – chejnik Feb 19 '16 at 6:58
• On page 7 of the geometry manual is a diagram of how layout is handled. The values for layouthoffset etc, are stored in \Gm@layouthoff etc. Since @ is used to make it difficult for users to break things, \makeatletter or \csname have to be used to write these names. The savebox is a safe way to insert a tikzpicture inside another tikzpicture. – John Kormylo Feb 19 '16 at 15:24
• I see. So you insert previously created whole picture using \savebox inside new tikz picture (well, nothing in it) with coordinate counted from layout variables. Many thanks for explanation. – chejnik Feb 20 '16 at 6:27
• Are the coordinate (0,0.5) in savebox doing something? Or the coordinates can have whatever value, because the picture is centered anyway? – chejnik Mar 3 '16 at 14:16
• Yup. An overlay image has no size, and the location depends on where the cursor was at the time. – John Kormylo Mar 3 '16 at 22:00