Change default image size with pdflatex

[stoffprof]

I would like to scale all images when generate a PDF. I can think of a few approaches, but am wondering if there's a simple option I could change in the _config.yml file instead.

Alternatives:

• generate latex and then manually add [scale=0.5] to all the \sphinxincludegraphics commands before compiling
• modify the Sphinx template (although I'm not exactly sure how best to do this)

Is there a simpler way to just set a preference for scale=0.5 somewhere?