I ran into the same issue, and was able to get PNG versions by using
pdfimages from the Poppler utils on the original PDF, with the
-png flag (and not the
-all flag), so that it outputs all the images in the PDF as PNGs.
This is because the
-png flag is not the same as the
-jbig2 flags (all of these are selected by
-png sets the output format, which is the default for all images to be output as, converting if necessary. Converting is actually the default for
pdfimages; with no format flags, it converts all images to PBM and PPM files.
-jbig2, on the other hand, specify not to convert images of those types, thus they are output in their original format. (Note that this means there's no option to convert images to JPEG in this program; only files stored as JPEGs are output as JPEG with the