Re: How to automatically figuring out the optimal resolution for a pdf file?

Theoretically, a PDF might contain raster images of various resolution. 
Practically speaking, however, this will seldomly be the case. In the 
easiest case, a PDF will just binds(scanned) TIFFs of one and the same 
resolution. If the PDF is produced by a printer driver or distilled fom 
a PostScript file, one will generally define fixed resolutions for 
raster images and black and white images.

So I guess there generally *is* something like an ideal resultion for an 
PDF when being converted to a raster image. But this is more of a 
Ghostscript problem than a problem of ImageMagick.

If your PDF just binds raster images, you should give pdfimages from 
Xpdf a try, which losslessly extracts them from the PDF, extracting the 
accordings streams.

Wolfgang Hugemann