How to figure out the resolution (DPI) of a PDF Document?
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I have a [PDFDocument][1] that also contains images. Now I want to know the resolution of these images. 

Fo the first step would be to somehow get the images out of the pdf document. But how?

Is that even possible with something provided in Cocoa? 


Thank you very much!


  [1]: https://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/QuartzFramework/Classes/PDFDocument_Class/Reference/Reference.html