dark contrast filter

[mike.foster]

Hi,

I'm looking for a free software that replicate 1DollarScan's fine tune capability, that converts a pdf file into one that is suitable for a particular e-reader, in my case, PRS-T2. What it does, basically, is margin removal, size file compression, greater contrast.

I tried Mac's Preview black & white filter but the quality falls way short of that of 1$scan's.

Calibre's pdf to pdf conversion by specifying Sony Reader in Output Profile does something quite different than the above as it does not preserve the text-to-page aspect ratio and it's not what I'm looking for.

Any suggestion?

Samples attached:
- 1$scan's Fine Tune for Sony ereader
- original pdf
- Preview's filter
- Fine Tune's filter

[mike.foster]

ps:

it seems K2PDFOPT might be able to do the job. But the default execution works similarly to Calibre (change of aspect ratio). Quite impressive, thought, but not quite what I want.

[mike.foster]

OK, I think it's just a matter of selecting the right option so mimic 1$scan's fine tue. The closest I found is 'mode' set to copy. But:
- the contrast is not as strong as FT
- The lower margin is not removed, unlike FT
- compression is 50% vs 90% with FT

...

[mike.foster]

This:

-cmax 2 -s -g 0.1 -wt -1 -mode tm

seemed fine, except no file size reduction!

[willus]

Your attachments got removed. Perhaps they were copyrighted material? Can you try attaching them again, or perhaps PM me a link to them?

[Glorfindel]

If they are copywrite than DO NOT attach them.

[mike.foster]

Originally Posted by willus

Your attachments got removed. Perhaps they were copyrighted material? Can you try attaching them again, or perhaps PM me a link to them?

Thanks for looking into it.

Here are temporary links to the attachment
- Original pdf (444kb)
- Preview's black & white filter (958kb)
- Fine tune's (58kb)
- k2opt / -cmax 2 -s -g 0.1 -wt -1 -mode tm (444kb)

[willus]

Originally Posted by mike.foster

Thanks for looking into it.

Here are temporary links to the attachment
- Original pdf (444kb)
- Preview's black & white filter (958kb)
- Fine tune's (58kb)
- k2opt / -cmax 2 -s -g 0.1 -wt -1 -mode tm (444kb)

Mike -- Try the command below. You can tinker with the values for -g and -cmax if you want (use a negative value for -cmax to force the contrast setting to that value). It's good to put -mode tm first--it sets a bunch of options internally, so then everything that comes after it can modify those options. Most importantly, though, the -mode tm command kicks k2pdfopt into "native output" mode, where it doesn't make use of contrast adjust, gamma correction, or sharpening, so your result did not actually use these. To fix this, you need to put -n- after -mode tm to turn that off. I then set the output dpi to 200 to match your source document. You don't need to specify -s since it's on by default. I've attached my result.

k2pdfopt -mode tm -odpi 200 -n- -g 0.4 -cmax 3 page22.pdf

[mike.foster]

Thank you!

The output file is 360kb with your parameters. If there was one parameter to change to bring down the file size closer to that of Fine Tune's (58kb), what would it be, and what value should I set it to?

I guess -odpi 100.

I'll go ahead and try that.

[mike.foster]

Originally Posted by mike.foster

Thank you!

I'll go ahead and try that.

It worked.

-odpi 60 to get to 56kb. More blurry than Fine Tune, though. I would do -odpi 100 which generates a file of size 109. That's 3/4 reduction.

[willus]

Originally Posted by mike.foster

It worked.

-odpi 60 to get to 56kb. More blurry than Fine Tune, though. I would do -odpi 100 which generates a file of size 109. That's 3/4 reduction.

For more ways to optimize the output file size, see my help page on the topic.

[markom]

Originally Posted by mike.foster

It worked.

-odpi 60 to get to 56kb. More blurry than Fine Tune, though. I would do -odpi 100 which generates a file of size 109. That's 3/4 reduction.

I don't care about file size on my PRS-T1 that much, why is it so important to you ?

I care about flipping speed, visual quality, 100% text accuracy and ability to use handwriting on every page without the need to leave landscape zoom for normal view before.

Those I can get using k2pdfdopt's modes.

In your case I've used whitetreshold -wt 70 function to reduce the file size a bit before (usually I use it in a case of poor contrast because of darker backgrounds) then -cmax 3 for better contrast and then default landscape(fitwidth) mode for Kindle that is not too far from Sony's screen dimensions.

I am also usually able to find a sweet spot using Sony's native contrast controls (adjust view, custom) only.

For a reduced pdf size those with Adobe Acrobat should try ClearScan OCR (example 2 in attachment), after applying whitetreshold -wt 70, and then gamma -g 0.3 or lower if this (default 0.5) was not dark enough.

[mike.foster]

Thank you.

That and using Willus' last piece of advice:

k2pdfopt mode tm -wt 70 -n- -g 0.4 -cmax 3 -bpc 1 page-22.pdf

works quite well. In fact, more crisp than Fine Tunes.

PS: doesn't speed of page flipping decrease with file size? Anyhow, I also keep a backup on my computer and have limited storage.

[mike.foster]

Hi all,

the last time we spoke, as I recall, the output of

k2pdfopt mode tm -n- -g 0.4 -cmax 3 page-22.pdf

was 1 page long. I tried again recently, and this command splits the input into segments, such that the output is 5 pages long.

I don't recall getting a new version of k2opt that could have been a possible reason for the change of behavior. I am at a loss to understand what is going on. Could someone please hint at a possible explanation?

[willus]

Originally Posted by mike.foster

Hi all,

the last time we spoke, as I recall, the output of

k2pdfopt mode tm -n- -g 0.4 -cmax 3 page-22.pdf

was 1 page long. I tried again recently, and this command splits the input into segments, such that the output is 5 pages long.

I don't recall getting a new version of k2opt that could have been a possible reason for the change of behavior. I am at a loss to understand what is going on. Could someone please hint at a possible explanation?

I think you just need a dash in front of "mode", like so:

k2pdfopt -mode tm -odpi 200 -n- -g 0.4 -cmax 3 page22.pdf