Set Tikz to size of page for layering

Question

I would like to create layers/overlays in my document (inline which may depend on variables\macros such as page number/chapter or user defined stuff).

How can I create a TikZ image that is the size of the page (without hard coding the values), with the ability to easily anchor to the edges of the paper (I think this will be already possibly with TikZ)?

Basically I want my TikZ picture's canvas to be that of the page with (0,0) being the top-left corner so I can do normal TikZ plotting on the page.

Obviously it should easily work with two-sided docs and it shouldn't interfere with normal page layout.

Thanks

Answer 1

You can use the \AddToShipoutPictureBG command from the eso-pic package together with a \put(0,0){ ...} to place your tikzpicture in the upper left corner of the page. Usually, for positioning TikZ objects relative to the page, one would use \tikz[remember picture, overlay] together with the (current page) node, but that requires two compile runs. This approach only needs one.

If you then set x=\paperwidth, y=-\paperheight, the coordinate (1,1) will be the lower right corner.

You can then position objects within your tikzpicture as usual:

\node at (0,1) [anchor=south west, scale=4] {Lower Left};
\node at (1,1) [anchor=south east, scale=4] {Lower Right};
\node at (0,0) [anchor=north west, scale=4] {Upper Left};
\node at (1,0) [anchor=north east, scale=4] {Upper Right};
%       \fill [ultra thick, orange] (0.5,0.5) circle [radius=2cm];
\draw (0,0) -- (1,1);

will produce

\documentclass{article}

\usepackage{tikz}
\usepackage{longtable}
\usepackage{afterpage}
\usepackage{lipsum}
\usepackage[texcoord]{eso-pic}

\begin{document}\lipsum[3]
\AddToShipoutPictureBG*{%
    \put(0,0){%
        \tikz [
            overlay,
            x=\paperwidth,
            y=-\paperheight] {
                \node at (0,1) [anchor=south west, scale=4] {Lower Left};
                \node at (1,1) [anchor=south east, scale=4] {Lower Right};
                \node at (0,0) [anchor=north west, scale=4] {Upper Left};
                \node at (1,0) [anchor=north east, scale=4] {Upper Right};
%
                \fill [ultra thick, orange] (0.5,0.5) circle [radius=2cm];
                \draw (0,0) -- (1,1);
        }
    }
}
\end{document}