[Tex/LaTex] Specify \svgscale instead of \svgwidth for Inkscape pdf_tex

Question

The image.pdf_tex documents created with Inkscape's PDF+LaTeX export use this code

  \ifx\svgwidth\undefined%
    \setlength{\unitlength}{293.02998953bp}%
    \ifx\svgscale\undefined%
      \relax%
    \else%
      \setlength{\unitlength}{\unitlength * \real{\svgscale}}%
    \fi%
  \else%
    \setlength{\unitlength}{\svgwidth}%
  \fi%

which makes it sound that instead of the usual

\def\svgwidth{15cm}
\input{image.pdf_tex}

you could do something like

\def\svgscale{0.2}
\input{image.pdf_tex}

However, it gives an error in pdflatex's output:

(.image.pdf_tex
! Undefined control sequence.
<argument> \unitlength * \real 
                               {\svgscale }
l.43 ...nitlength}{\unitlength * \real{\svgscale}}
                                                  %
?

How can I make this work?

The reason is that I want to include to vector graphic subfigures that have different sizes, but at should be displayed at the same scale.

Answer 1

The package is using calc package syntax so add

\usepackage{calc}

to your document.