If tess4 renderer needed to skip OCR on a page it would end up
duplicating the page contents onto the new page, rather than creating
a blank OCR layer and placing it on the output page. This created
duplicated content in output files.
Ghostscript 9.21 does not seem to accept Unicode above U+FFFF. Previous
versions did, but it now exits with a rangecheck error (-15).
Reject on the command line for now. Complete fix would also need to
check input PDF’s metadata.
At recommendation of Artifex people, don’t use the filename pdfa_def.ps
because if given without a full path Ghostscript will prioritize
searching its own resources over the current directory, and will pick up
the example file pdfa_def.ps instead. We used the full path anyway,
but this is a prudent defensive change to avoid odd Ghostscript behavior.
At least on macOS with my quadcore performance improves with two
tesseracts in parallel (20% gain). Hard to say how this will affect
Linux, but stepping up to 2 jobs seems justifiable.
It seems that Tesseract v4 on a platform with OpenMP working correctly
while perform poorly with ocrmypdf because each will also soak up all
available CPUs. Running N^2 processes/threads on a N-core CPU where
each wants 100% of CPU turns out to be detrimental.
So, we restrict ocrmypdf w/tessv4 to a single Tesseract process at a
time, for now. Alternative may be to limit OpenMP threads if throughput
is higher.
Because ruffus doesn’t handle exceptions well I tended to call sys.exit
to make sure we got out of dodge when needed. However, sys.exit is not
ideal for the Python API this is moving towards, so this introduces
proper exceptions for the various cases that retain suggested error
codes. Only __main__.py should call sys.exit now, everyone else has to
throw an exception.
For now the worker raising a fatal exception is logging messages rather
than passing an exception object with the fatal error message, mainly
because ruffus doesn’t properly marshall the exception object so we
just check “what is the name of the exception class that caused ruffus
to thrown an RethrownJobError”?
Also fixed along the way was the wrong return code being shown for
encrypted PDF checking, and incorrect use of str.find (e.output.find)
in boolean logic (str.find returns -1 on failure to find, which is True).
This leaves __main__.py to handle command line arguments while pipeline.py
runs the pipeline - mostly. They are still somewhat intertwined, with
__main__.py doing essential things for pipeline.py, etc., and some
helper functions that could go in their own module.
All tests pass after this major refactor.
Redirect stderr->stdout to hopefully make GS output easier to work with
overall, since the previous code didn’t seem to account for mixed used
properly.
As of 3.1.1, our minimum version, these codecs are now required by
default for a successful installation, effectively solving the problem
of Pillow installed without libjpeg/libpng.
James R. Barlow
Tomandjbarlow83