k2pdfopt: optimizes PDFs for viewing on e-readers - Page 146

StarSlayer · 06-17-2026, 02:23 AM

Quote:

Originally Posted by Darthdader

@willus I couldn't find your email via about → e-mail [an error occurred while processing this directive]
But, it appears whatever you're using for captcha for downloads isn't working. I've tried it on 3 different machines (mac-os on chrome, windows on firefox, mobile chrome. No ad-blockers or vpn. Tried on wifi and mobile network) and no-show, 500 error inspecting. Unfortunately can't download it at this time :^(

Similar issue for me as well captcha wont load

willus · 06-21-2026, 01:32 PM

I've fixed the k2pdfopt download page. Sorry for the inconvenience.

hjcj77 · 07-15-2026, 07:24 PM

Quote:

Originally Posted by willus

I've fixed the k2pdfopt download page. Sorry for the inconvenience.

Hello,

I'd like to thank you for the very unique work you put in. However the website appears to be dead as i get 404s from every device and connection I tried. Would you mind taking a look? Thanks

willus · 07-17-2026, 12:09 PM

It seems to be working now. I just tried it.

Shohreh · 08-04-2026, 10:17 AM

What settings would you recommend I try to make reading the attached scanned book as painless as possible on a Kobo Clara BW?

… after splitting each picture/page in half using the following command:

Code:

mutool.exe poster -x 2 "input.pdf" "output.pdf"

--
Edit: Pretty good

Code:

k2pdfopt.exe -grid 2x1 -mode fw -ls- -om 0.2 -w 758 -h 1024 -dpi 213 -fc- input.pdf

isaacbh · 08-27-2026, 01:31 PM

I tried the latest version in Fedora 44, but it crashes when trying to process a file. I tried the "old cpu" version too, although I have a newish computer. It always segfaults after the massage "Detecting document orientation". I then attempted to compile from source, but tbh it's over my head. I used to use this program a lot on Windows, I hope to continue using it on Linux. Note: it does NOT crash when in the text ui (selecting options) but it crashes once processing begins.

Edit: I narrowed it down to the -ci option. Using an integer with this option will crash the program. Specifying a filename (even the file being processed) is fine. This problem might not be Linux specific.

willus · 09-01-2026, 01:05 PM

Quote:

Originally Posted by isaacbh

Edit: I narrowed it down to the -ci option. Using an integer with this option will crash the program. Specifying a filename (even the file being processed) is fine. This problem might not be Linux specific.

Following -ci with an integer only appears to be a bug. It crashes on Windows also. I'll add to my bug list. Thanks.

willus · 09-01-2026, 01:18 PM

Quote:

Originally Posted by Shohreh

Edit: Pretty good

Code:

k2pdfopt.exe -grid 2x1 -mode fw -ls- -om 0.2 -w 758 -h 1024 -dpi 213 -fc- input.pdf

Yeah--that looks pretty good to me as long as you find it readable. Sorry for the delayed reply! If you want, you can try -n- to turn off native mode and maybe -cmax 3 to increase the contrast and experiment with gamma settings (e.g. -g 0.7) to get the text blackness where you want it. Using -n- will make the file output size (in bytes) larger.

isaacbh · 09-01-2026, 05:26 PM

Thanks for looking into the ci bug. I wanted to ask, what processing gets done on the cover image besides resizing it? I would very much like the option to turn off any processing on the cover image aside from resizing it if needed, including leaving it in color even if the rest of the pages are output in grayscale. It would look nice on a color ereader.

07-17-2026, 12:09 PM	#2179
willus Fuzzball, the purple cat Posts: 1,321 Karma: 11087510 Join Date: Jun 2011 Location: California Device: iPad	It seems to be working now. I just tried it. Last edited by willus; 07-17-2026 at 12:37 PM.

08-27-2026, 01:31 PM	#2181
isaacbh Connoisseur Posts: 63 Karma: 201178 Join Date: Mar 2015 Device: Kobo Aura H20, Kobo Forma, Kindle Paperwhite 12	I tried the latest version in Fedora 44, but it crashes when trying to process a file. I tried the "old cpu" version too, although I have a newish computer. It always segfaults after the massage "Detecting document orientation". I then attempted to compile from source, but tbh it's over my head. I used to use this program a lot on Windows, I hope to continue using it on Linux. Note: it does NOT crash when in the text ui (selecting options) but it crashes once processing begins. Edit: I narrowed it down to the -ci option. Using an integer with this option will crash the program. Specifying a filename (even the file being processed) is fine. This problem might not be Linux specific. Last edited by isaacbh; 08-29-2026 at 04:22 PM.

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06-21-2026, 01:32 PM	#2177
willus Fuzzball, the purple cat Posts: 1,321 Karma: 11087510 Join Date: Jun 2011 Location: California Device: iPad	I've fixed the k2pdfopt download page. Sorry for the inconvenience.

09-01-2026, 05:26 PM	#2184
isaacbh Connoisseur Posts: 63 Karma: 201178 Join Date: Mar 2015 Device: Kobo Aura H20, Kobo Forma, Kindle Paperwhite 12	Thanks for looking into the ci bug. I wanted to ask, what processing gets done on the cover image besides resizing it? I would very much like the option to turn off any processing on the cover image aside from resizing it if needed, including leaving it in color even if the rest of the pages are output in grayscale. It would look nice on a color ereader.