Does anyone know how to extract a background from a powerpoint ppt file? I have been googling about it and I read something about a slideshow master, but I don't see it anywhere.
I am running Microsoft PowerPoint 2008 on Mac.
You'll probably have to use Applescript to do the job if you intend to automate this. PPT 2008 lacks VBA. MacTech magazine has a thorough guide to automating Office 2008 via Applescript on their site, by the way.
In practice, if you know which slide's background you want to extract, and assuming you want to extract it as an image, you'd create a duplicate of the slide, delete all of the shapes on the slide (which'd leave just the background graphics), then use the Slide.Export method to save an image file at whatever resolution you need, up to 3000 pixels wide or so.
If there's any way to bag 2008 and use 2011 instead, life will be simpler and you'll leave it with more hair intact. ;-)