Thread: Optimize PDFs from archive.org for E-Ink devices
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Old 02-29-2020, 07:19 PM   #21
j.p.s
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Quote:
Originally Posted by willus View Post
I am realizing that in the original post for this thread, there were two different versions of the PDF--the black and white one (which I processed with my original post in this thread), and the yellowed version. To process the yellowed version, I needed to jack up the contrast quite a bit. I've tweaked this set of options to give one output page per input page--simply cropping each input page:

k2pdfopt -mode tm -c- -rt 0 -cmax -8 -bpc 2 -n- -dr 2 -ac yellowed.pdf -o processed.pdf

The "-mode tm" does the one page per page bit. "-cmax -8" to use a fixed contrast adjust on each page (the default auto adjust isn't aggressive enough for this document--you could probably stand to go even higher than 8). The "-dr 2" bumps up the output resolution by a factor of two over what it would normally be for a Kindle Paperwhite. Example input and output attached.
One form of archive.org book files have a mask image for each page that can be used to make white regions of the page completely white. Have you ever used those to help clean up the page?
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