# [Tex/LaTex] \includegraphics optional argument not resolved if macro

graphicsmacros

\documentclass[a4paper,10pt,twoside]{book}
\usepackage[demo]{graphicx}

\begin{document}

\newcommand{\scalefactor}{scale = 0.25}

\begin{figure}[!ht]
\centering
%Next line does not work
\includegraphics[\scalefactor]{image}
% The following line works
%\includegraphics[scale = 0.25]{image}
\end{figure}

\end{document}


Output:

! Package keyval Error: scale = 0.25 undefined.


I need to scale a number of images by the same factor, hence the command.

1. How to solve this and more importantly
2. Why is this only specific to \includegraphics

\newcommand{\scalefactor}{.25}