[Tex/LaTex] Using \put command relative to page size

beamerdiagramspdfpagespicture-mode

I want to include a logo in the pdf pages included in Beamer.

I tried writing macro and progressed so far. 

\documentclass[fleqn,xcolor=dvipsnames]{beamer}

\newlength{\logosize}
\setlength{\logosize}{7.50mm}

\newlength{\logoXinpdf}
\newlength{\logoYinpdf}
\setlength{\logoXinpdf}{0.9\textwidth}
\setlength{\logoYinpdf}{0.8\textheight}


\usepackage{pdfpages}

\def\getpdfpages#1#2{\begingroup
  \setbeamercolor{background canvas}{bg=}
  \includepdf[pages={#1},picturecommand={\put(\logoXinpdf,\logoYinpdf){\pgfimage[width=\logosize]{mylogo}}}]{#2}
  \endgroup}


\begin{document}


\getpdfpages{{9,12}}{mypdf.pdf}


\end{document}

However, when I run pdfLaTeX, I get an error in the line of,

! A <box> was supposed to be here.
<to be read again> 
                   \unitlength 
l.23 \getpdfpages{{9,12}}{mypdf.pdf}

I understand that the problem is with the \put command. If I replace the \logoXinpdf,\logoYinpdf lengths with absolute numbers, everything works fine.

Is there a way I can use these defined lengths with the \put command?

Best Answer

It's actually sufficient just to locally disable \unitlength (assuming this is a picture mode command internally.

\def\getpdfpages#1#2{\begingroup
  \setbeamercolor{background canvas}{bg=}
  \includepdf[pages={#1},picturecommand={{\def\unitlength{}\put(\logoXinpdf,\logoYinpdf){\pgfimage[width=\logosize]{mylogo}}}}]{#2}
  \endgroup}

\put expects a multiplier and does essentially 

\setlength\something{#1\unitlength}
\setlength\somethingelse{#2\unitlength}

So if \unitlength is empty it is OK to pass lengths to put. Heiko's picture package takes this a bit further and adds some conditional logic so that you can use either a length or a multiplier, so that \unitlength becomes essentially a default unit. So it is probably enough just to load picture and make no change to your code.

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