Appears to be necessary to disable each state of the pipeline that is
inactive, not just initial and terminal stages of an inactive segment.
If nothing else this makes what is going on more explicit.
pdftoppm in recent versions (0.26.4,5) seems to be incapable of
producing valid TIFFs, so have it dump a .pnm file and let ImageMagick
figure out how to convert it to TIFF. This is not ideal, but at least
it works.
convert .pnm -deskew <...> .pnm seems to have a bug that produces an
invalid .pnm file which later causes tesseract (specifically,
leptonica) to choke (using 3.02/1.71 as versions, respectively). Will
change pipeline to use tiffs internally since they are less stupid.
Put TESS_CFG_FILES last because it is optional and can be blank. If
omitted it breaks the sequence of subsequent parameters. Also cleanup
text output in this new mode.
If a page contains font data, the script would abort, unless -f was given,
in which case it would use pdftoppm to rasterize the font into a bitmap
and then attempt to OCR it. -f is almost certainly not what users want
unless they want to debug OCR or something.
If a PDF already has fonts it either was OCR'd already, or it is
a composite file containing, for example, some scanned documents appended
to a text report. In the latter case, this -s option provides OCR on
pages that don't have it without changing those that do, and if a PDF
was completely OCRed it will be converted to PDF/A. In batch jobs with
a mix of OCR and non-OCR the implicit conversion to PDF/A is also useful.
When I upgraded to poppler 0.24.5, pdftoppm was not compiled because the
script had --disable-splash-output set for some reason.
For OS X Homebrew the solution is:
brew uninstall poppler
brew install poppler --with-splash-output
Allow tesseract 3.02.01 to be used.
Even 3.02.01 fails in few cases (see issue #28). I decided to allow this
version anyway because 3.02.02 is not yet available for some widespread
linux distributions
Jim Barlow
fritz-hh
Dorian Scholz
Martin Ettl
MoritzFago
Andy Signer
Andreas Christ