pdfimages is nice as it does not reencode but only extract jpegs. But there is a bug:
pdfimages comes from package "poppler-utils" or from the bigger "xpdf-utils". At least in Ubuntu "poppler-utils" comes already pre-installed. The pdfimages in poppler-utils 10.0.3 (Ubuntu 9.04 Jaunty) still does not react to the option "-j" to extract ".jpg". It always extracts ".ppm".
As a workaround you may replace "poppler-utils" with "xpdf-utils":
$ sudo apt-get install xpdf-utils
with kind regards,
+++ Oliver
