unpaper doesn't seem to be good at deskewing. It fails on test case
with a lot of italics. I think it also struggles on pages with a lot
of whitespace. Leptonica continues to shine here.
However, this is only a first crack at Leptonica. The leptonica module
should be redone to use cffi (more extensible).
Also considering the possibility of making all Lept calls in a forked
process to insulate the calling process from C code crashes and the
messy redirect of stdout/stderr to read Leptonica's errors.
I don't think the redirect is a huge problem as long as multiprocesses
rather than multithreads are used. The ruffus child process that is
handling a page is single threaded and will not be affected by the
redirection. It just feels dirty. The main reason to consider a child
process is crash isolation.
Add -f to force generation of the background image at the desired
oversample resolution. Our new behavior is to only send the oversampled
image to Tesseract while leaving the main page intact unless asked to
deskew, clean, etc.
Ruffus treats omitted parameter as -j1. For our purposes it makes more
sense for omitting the parameter to mean "use all CPUs". As such we
must be able to distinguish -j1 from the parameter -j being omitted.
Telling ruffus to ignore the argument actually just makes it not auto
generate the argument. We can add an argument back with the same name.
Because we don't really use ruffus checkpoint feature, putting the
database in a permanent location does not help anything, but does cause
large database files and problems if the .ruffus_history.sqlite wanted
to be in a writable location.
qpdf won so hard it wasn't funny, even though it must be called once
per page to do the job. Perhaps Ghostscript interprets it as a call to
render the page?
time bash qpdf-test.fish ../tests/resources/multipage.pdf
0.07 real 0.02 user 0.03 sys
time gs -sDEVICE=pdfwrite -dSAFER -o '%06d.pdf' ../tests/resources/multipage.pdf
5.12 real 5.06 user 0.04 sys
James R. Barlow