k2pdfopt: optimizes PDFs for viewing on e-readers

[poco06]

Hello,
Just discover K2pdfopt and would like to know if there is a specific parameter to use for this case :

I have comics in pdf but with large page size (A4) and global size of more than 100Mo
I would like to reduce the page size to Ipad size but keeping the way pages are done (ie : page 4 will still be page 4 with all items in it but with reduced size). Normally, file size shoudl reduced to 20Mo !

Can you help please?
Thanks
Pat

[willus]

Originally Posted by poco06

I have comics in pdf but with large page size (A4) and global size of more than 100Mo
I would like to reduce the page size to Ipad size but keeping the way pages are done (ie : page 4 will still be page 4 with all items in it but with reduced size). Normally, file size shoudl reduced to 20Mo !

Can you help please?

Generally you want to use either

k2pdfopt -mode copy -odpi 180 ...

or

k2pdfopt -mode trim -n- ...

The first option will keep the page sizes exactly the same as the source PDF, but you can change the dpi of the output pages to whatever resolution you want using the -odpi option (lowering the value will reduce the total output file size in MB but will reduce the resolution of each page). To make the best use of iPad's 1536 x 2048 screen with an A4 image, you want to use about 180 dpi.

The second option will get rid of any excess margins on each page, cropping it only to the visible content.

[dudebro]

Holy shit this is the best thing ever, I can finally read those shitty 2-column articles without going crosseyed, I've tried dozens of pdf apps for Android and none do this kind of thing. WELL DONE.

Just a suggestion, I would love a reader on Windows (or a plugin for Sumatra PDF) that does this automatically when I open pdf files so that I don't have to convert everything beforehand (amazingly, conversion to mobile layout makes things WAY more readable even on a laptop screen!)

Anyways, thanks again for this software and I hope whoever invented the 2-column journal format burns in hell for eternity

[willus]

Originally Posted by dudebro

Holy shit this is the best thing ever, I can finally read those shitty 2-column articles without going crosseyed, I've tried dozens of pdf apps for Android and none do this kind of thing. WELL DONE.

Just a suggestion, I would love a reader on Windows (or a plugin for Sumatra PDF) that does this automatically when I open pdf files so that I don't have to convert everything beforehand (amazingly, conversion to mobile layout makes things WAY more readable even on a laptop screen!)

Anyways, thanks again for this software and I hope whoever invented the 2-column journal format burns in hell for eternity

I'm not much in the business of writing plugins or reader apps. I only know of the reader apps I mention on my 3rd-party contributions page. I might poke into what it would take to make a plug-in for Sumatra, though.

Sorry--can't agree with you on the 2-column format. I actually prefer it for reading journal articles on a normal page-sized format. Besides, it gave me a nice project to work on. Thanks for the enthusiastic feedback.

[eschwartz]

You can build a desktop emulator for KOReader if you set up the development environment. KOReader embeds k2pdfopt for on-the-fly reformatting on ereaders, but there are no prebuilt binaries for the desktop.

That might be too much work to be worth the effort, though.

[poco06]

Hello,

I'm using K2pdf with your recommandation concerning the parameters (k2pdfopt -mode copy -odpi 180) to use for downsizing the pdf size and it's woorking fine. Thanks.
Now, when I look at the result, I'm not really happy with the colors.
In fact, the original pdf have pastel colors and the optimized pdf have very strong colors.
Is there a way to make the optimized version the same color look as the original?
Regards
Pat

[willus]

Originally Posted by poco06

Hello,

I'm using K2pdf with your recommandation concerning the parameters (k2pdfopt -mode copy -odpi 180) to use for downsizing the pdf size and it's woorking fine. Thanks.
Now, when I look at the result, I'm not really happy with the colors.
In fact, the original pdf have pastel colors and the optimized pdf have very strong colors.
Is there a way to make the optimized version the same color look as the original?
Regards
Pat

Yes--you can turn off gamma correction and contrast adjustment (which default to values that darken the text on the kindle):

-cmax 1 -g 1

[poco06]

Hi Willus
That's perfect
Many thanks
Pat

[moll]

I am using the software on Mac and it is great.

However, for some PDF files, I met the error "Segmentation Fault 11" and the process terminated. It is not very convenient while converting a folder.

Please

[willus]

Originally Posted by moll

I am using the software on Mac and it is great.

However, for some PDF files, I met the error "Segmentation Fault 11" and the process terminated. It is not very convenient while converting a folder.

Please

Welcome to MobileRead. Can you post one of the PDFs that causes the segmentation fault so I can test it? If you don't want to post it publicly, send me a private message.

[moll]

Originally Posted by willus

Welcome to MobileRead. Can you post one of the PDFs that causes the segmentation fault so I can test it? If you don't want to post it publicly, send me a private message.

I realised that, if I convert this PDF file again, the segmentation fault disappeared, i.e. the error appears only with batch conversion.

[isaacbh]

Hi willus..
Figures and diagrams are often accompanied by a caption. However, k2pdfopt will not treat the caption text as part of the figure and so the caption might end up on the next page if a break occurs. (This is understandable, since the caption is just text.) To circumvent this, I put colored marks before and after the figure + caption and use -bpm2 to keep them together. This works, however now there is no vertical space between the caption and the next paragraph, as seen in the image. Is there some magic that k2pdfopt can do to restore that space? Or maybe a solution is to be able to mark figures manually: That would allow also tables and lists to be treated as a single unit, if desired.

[willus]

Originally Posted by isaacbh

Hi willus..
Figures and diagrams are often accompanied by a caption. However, k2pdfopt will not treat the caption text as part of the figure and so the caption might end up on the next page if a break occurs. (This is understandable, since the caption is just text.) To circumvent this, I put colored marks before and after the figure + caption and use -bpm2 to keep them together. This works, however now there is no vertical space between the caption and the next paragraph, as seen in the image. Is there some magic that k2pdfopt can do to restore that space? ...

I'll have to see why the white space captured between marks for -bpm2 gets eliminated. My opinion is that it should be maintained, so I'd say that's a bug. But you can kludge it with the existing version by putting a small black mark just above the second colored mark that keeps the caption with the figure. See that attached example. BTW, k2pdfopt does try to anticipate captions after figures and keep them with the figures, but it has some internal rules for how close it expects the captions to be to the figures, and if those internal rules are violated, then the caption can get separated from the figure.

[isaacbh]

Originally Posted by willus

But you can kludge it with the existing version by putting a small black mark just above the second colored mark that keeps the caption with the figure.

Thanks, that helped! Hope it gets fixed, as its a bit tedious now

[atoq]

Hi Willus,

I'm using k2pdfopt 2.34b for converting pdfs to be read on Nook.
The conversion is fine, but when a line contains an equation, and ends
on equal sign, =, for being continued on the next line, the equal sign
gets removed in the converted pdf.