I use Babel to create UML diagrams using plantUML. The codeblocks produce png files. 

When exported to LaTeX, the png files are imported using \includegraphics. The width is set to 0.9\linewidth

Instead specifying the width, I'd like to use the parameter \scale.

Ideally, I would set \scale in the document header, possibly over-riding the setting when necessary.

Is this possible, and if so, can you point me to the documentation? I could not find any.

Thank you,

Mirko